UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  265 
June,  1923 

PLANT  DISEASE  AND  PEST  CONTROL 

BY 

W.  T.  HOENE,  E.  O.  ESSIG  and  W.  B.  HEKMS 


TABLE  OF  CONTENTS 

Diseases  and  insect  pests  of  crops,  alfalfa  to  walnut 1-51 

General  subjects  (troubles  of  many  crops) 53-60 

Household  pests  and  animal  parasites 60-69 

Formulas    70-96 


ALFALFA 

Crown  Wart,  Urophlyctis  alfalfas  (Lag.)  Magn. — Crown  wart 
was  formerly  called  crown  gall,  but  is  not  connected  with  true  crown 
gall  (see  general  subjects,  p.  55).  Rounded  irregular  tumors  develop 
near  the  surface  of  the  ground  and  some  plants  may  subsequently 
die.     Widely  distributed,  but  not  often  destructive  in  California. 

Dodder  or  Love  Vine,  Cuscuta  sp. — Yellowish  threads  grow  up 
and  entwine  the  plants,  causing  serious  injury.  This  is  a  parasitic 
plant  with  minute  flowers  and  with  seeds  similar  in  size  to  alfalfa  seeds. 
Avoid  seed  in  which  dodder  occurs.  The  State  Department  of  Agri- 
culture, Sacramento,  maintains  a  laboratory  for  testing  seeds,  to 
which  samples  may  be  sent.  Small  patches  may  be  killed  by  mowing 
and,  when  dry,  burning  with  additional  material  or  kerosene.  After- 
wards resow  the  spot.  Badly  infested  fields  should  be  plowed  up. 
In  the  drier  sections  it  is  reported  that  dodder  may  be  killed  by  keep- 
ing the  field  dry  for  a  time,  as  alfalfa  will  endure  more  drought  than 
dodder. 

Downy  Mildew,  Peronospora  trifoliorum  De  Bary. — Upper  leaves 
become  partly  yellow  with  the  edges  turned  down.  The  lower  sides 
of  the  leaves  have  a  fuzz  which  turns  violet.  Very  common  in  winter 
and  spring.     Not  destructive. 


Z  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Leaf  Spot,  Pseudopeziza  medicaginis  (Lib.)  Sacc. — Small  dark 
spots  appear  on  the  leaves,  which  fade  and  drop  early  if  spots  are 
numerous.  The  commonest  and  most  universal  trouble  of  alfalfa 
in  California.  Favored  by  moist  atmosphere,  and  worst  on  weak 
plants  in  dry  soils  under  unfavorable  growing  conditions.  Fre- 
quently causes  loss  of  nearly  all  the  leaves.  Normally  disappears 
after  cutting  and  good  irrigation. 

Rust,  Uromyces  striatus  Schr. — Powdery  dark  brown  dots  appear 
on  the  leaves. 

Stem  Rot  or  Wilt,  Sclerotinia  libertiana  Fcl. — Stem  rot  is  caused 
by  the  same  fungus  as  cottony  rot  of  lemons,  green  rot  of  apricots, 
fig  die  back,  etc.  Vetch  and  various  leguminous  cover  crops  are 
attacked.  Moist  weather  favors  it.  Stems  rot  off  near  the  surface 
of  the  ground  and  the  affected  part  becomes  covered  with  a  cottony 
snow-white  mold.  Irregular  black  bodies  as  large  as  popcorn  grains 
form  in  protected  places  about  and  in  the  diseased  stems. 

Treatment  of  foliage  diseases  of  alfalfa  in  California  has  gen- 
erally been  confined  to  mowing  the  diseased  stand  and  applying 
water  if  that  is  needed.  Sometimes  the  ground  is  disked  or  treated 
with  a  renovator.  Early  mowing  may  dispose  of  a  diseased  and  weedy 
crop  which  may  be  used  for  silage,  or  if  too  bad  for  this  purpose, 
such  a  crop  makes  good  orchard  mulch.  Where  the  stand  becomes 
too  thin  or  uneven,  it  should  be  plowed  up  and  resown.  Perhaps 
no  crop  is  more  dependent  on  proper  soil  preparation  and  treat- 
ment. Consult  your  local  farm  advisor,  or  write  to  the  University 
of   California,   College  of  Agriculture. 

Alfalfa  Caterpillar,  Eurymus  eury theme  (Boisd.). — The  caterpil- 
lars are  about  one  inch  long  and  dark  green  in  color  with  a  distinct 
and  often  a  pale  white  or  yellow  line  on  each  side.  They  feed  on  the 
leaves  and  may  entirely  defoliate  the  plants.  The  yellow  butterflies 
may  be  seen  in  great  numbers  hovering  over  the  fields.  Cutting  as 
soon  as  the  caterpillars  appear  in  destructive  numbers,  followed  by 
irrigation,  is  the  best  method  of  control. 

Armyworms,  Cutworms,  Grasshoppers,  etc. — See  "General  Sub- 
jects," p.  53. 

Clover  Seed  Chalcis  (Bruchophagus  funebris  How.). — The  small 
white  larvfa  of  this  insect  is  just  large  enough  to  fill  the  seed.  It 
occurs  in  sufficient  numbers  to  greatly  reduce  the  seed  crop  in  most 
localities  in  the  state.  Destroying  all  the  seed  heads  during  winter 
and  the  straw  after  threshing  will  greatly  reduce  the  infestation  for 
the  next  year. 


Circular  265]  PLANT  DISEASE  AND  PEST   CONTROL  3 

ALMOND 

Armillaria,  Crown  Gall,  Sour  Sap. — See  "General  Subjects." 

Rust,  Transclielia  punctata  (Pers.)  Arih.=Puccinia  pruni. — Pow- 
dery dark  brown  dots  appear  on  the  leaves  in  summer  and  autumn. 
Also  on  prune,  plum,  peach,  and  apricot.     No  control  is  known. 

Shot-hole,  Coryneum  beijerinckii  Oud. — Principally  due  to  peach 
blight  fungus.  Small  spots  are  killed  on  the  young  rapidly  expand- 
ing leaves,  the  living  part  draws  away  from  the  dead  area  and  the 
latter  drops  out.  Young  fruits  are  also  attacked  and  may  drop. 
There  may  be  much  injury  and  loss  both  of  fruit  and  foliage.  Spray 
with  lime-sulfur  1-10  just  as  the  buds  are  swelling. 

Unfruitfulness. — Usually  due  to  frost  or  to  rain  at  blooming 
time,  or  to  lack  of  a  suitable  mixture  of  varieties  for  cross  pollination 
(most  varieties  are  self -sterile),  or  to  the  lack  of  bees  for  carrying 
pollen,  or  to  weakness  from  red  spider  or  other  injury  the  previous 
year.  The  selection  of  suitable  soils  and  thermal  belt  situations 
offer  some  difficult  problems  for  the  almond.  See  "Frost"  under 
"General  Subjects,"  p.  55. 

California   Peach  Borer. — See   "Peach." 

Peach  Twig  Borer.— See  "Peach." 

Red  Humped  Caterpillar. — See  ' '  Prune. ' ' 

Red  Spider  or  Almond  Mite,  Bryobia  praetiosa  Koch. — The 
largest  orchard  mite,  nearly  the  size  of  a  pinhead ;  brownish  or  green- 
ish with  reddish  legs,  the  front  pair  as  long  as  the  body  and  much 
longer  than  the  other  legs.  The  bright  red,  globular  eggs  are  laid  in 
great  numbers  on  the  limbs  and  twigs  of  the  trees,  where  they  remain 
through  the  winter  and  hatch  in  the  spring.  Spray  the  trees  in 
the  winter  (January  and  February)  with  lime-sulfur  1-10  or  crude 
oil  emulsion  (Formula  18)  to  destroy  the  eggs.  To  control  the  mite 
during  the  growing  period  of  the  trees  apply  dry  sulfur,  sulfur 
paste,  wettable  sulfur  sprays  (Formula  13  or  14),  or  lime-sulfur 
1-50  plus  5  pounds  of  wettable  sulfur  as  soon  as  the  mites  appear 
in  the  spring  and  as  often  as  necessary  during  the  summer  and  fall. 
(See  Bull.  No.  347.) 

San  Jose  Scale. — See  "Apple." 


4  university  of  california experiment  station 

Combined  Spraying 

Lime-sulfur  spraying  when  the  buds  are  swelling  will  control  shot- 
hole  fungus  and  peach  twig  borer,  and  help  to  destroy  San  Jose  scale 
and  the  eggs  of  the  almond  mite.  Crude  oil  emulsions  will  also 
destroy  scale  insects,  almond  mite  eggs,  and  will  arrest  some  of  the 
fungus  diseases  when  applied  as  a  dormant  spray. 

APPLE 

Blight,  Bacillus  amylovorus  (Burr.)  De  T. — See  "Pear."  Re- 
move all  worthless  apple,  pear,  and  quince  trees  near  apple  or  pear 
orchards.  Christmas  berry,  Cotoneaster,  loquat,  and  related  wild 
or  ornamental  plants  should  be  watched  for  blight.     See  ' '  Pear. ' ' 

Mildew,  Sphaerotheca  leucotricha  (E.  &  E.)  Salm.  &  S.  oxyacan- 
thae  (De  C.)  De  B. — A  white  powdery  growth  covers  leaves  and 
shoots,  causing  stoppage  of  growth  and  distortion.  Where  abundant 
the  tree  is  weakened.  Especially  serious  in  foggy  sections.  Cut 
out  mildewed  twigs  as  thoroughly  as  possible  in  winter.  Use  lime- 
sulfur  for  scab  spraying  (See  "scab")  or,  if  scab  is  not  serious,  use 
sulfur  paste,  16  pounds  to  200  gallons  of  water  (or  home-made 
wettable  sulfur  spray,  Formula  13  or  14)  when  petals  are  falling. 
Later  spraying  for  mildew  may  be  done  with  the  same  material. 
Sulfur  sprays  cause  injury  to  apple  trees  in  some  sections. 

Sappy  Bark,  Polystictus  versicolor  (L.)  Fr. — Bark  puffs  up  in 
winter  about  wounds  and  dries  out  later,  becoming  loose  and  papery. 
Recurs  in  succeeding  winters,  causing  death  of  limbs  and  general 
breakdown  of  trees.  Caused  by  wood  decay  in  the  interior  of  the 
tree.  Avoid  large  wounds  or  protect  them  with  a  covering  of  asphalt. 
See  "Wood  Decay"  under  "General  Subjects." 

Scab,  Venturia  inequalis  (Cke.)  Wint.  —  Fusicladium. — Velvety 
dark  moldy  patches  on  young  fruit  and  sometimes  on  leaves  and 
twigs,  rough  corky  spots  on  mature  fruit,  with  distortion.  Spray 
with  Bordeaux  mixture  (Formula  9)  or  lime-sulfur  1-20,  just  as 
winter  buds  open.  Again  with  lime-sulfur  1-35  when  petals  are 
falling.    Bordeaux  applied  after  the  bloom  may  russet  the  fruit. 

Codling  Moth,  Cydia  pomonella  (Linn.). — The  common  white  or 
pinkish  worm  or  caterpillar  nearly  one  inch  long  is  found  inside 
the  fruit.  For  control,  spray  from  two  to  five  times  as  needed.  First 
spray  should  be  applied  as  the  petals  are  falling,  using  2y2  pounds 
powdered  or  5  pounds  paste  arsenate  of  lead  to  100  gallons  of  water ; 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  5 

the  second  spraying  should  be  made  three  weeks  later  using  the 
same  strength.  The  remaining  applications  should  follow  as  needed, 
but  should  be  somewhat  weaker,  2  pounds  of  powdered  or  4  pounds 
of  paste  arsenate  of  lead  to  100  gallons  of  water.  Cover  with  a  fine, 
fog-like  spray.  For  a  spreader  use  1  pound  of  dry  casenite  or  bill- 
board paste  to  100  gallons  of  spray  material.  Also  see  " spreaders" 
under  "General  Subjects." 

Flat-headed  Apple  Tree  Borer,  Chrysobothris  mali  Horn. — The 
full-grown  larvae  or  borers  are  white  or  pale  yellow  and  vary  from 
one-half  to  three-quarters  of  an  inch  in  length.  The  portion  just 
behind  the  head  is  greatly  enlarged  and  flattened,  a  character  which 
is  responsible  for  the  common  name.  The  adult  beetles  lay  eggs  on 
sunburned  or  other  dead  areas  of  the  trunk.  Whitewash  trunks  to 
prevent  sunburn  and  repel  egg-laying.  Avoid  injuries  and  wounds. 
Dig  out  borers  and  paint  with  asphaltum. 

Fruit  Tree  Leaf  Roller,  Archips  ■  argyrospila  Walker. — The  eggs 
are  laid  in  small,  flat,  grayish  or  brownish  masses,  usually  on  the  new 
growth  near  the  tops  of  the  trees,  in  the  fall.  They  hatch  in  the 
spring  and  the  caterpillars  draw  the  leaves  together  into  compact 
rolls  in  which  they  live,  and  from  which  they  wriggle  violently  if 
disturbed.  When  mature  the  larvae  are  nearly  three-quarters  of 
an  inch  long,  deep  green,  with  the  head  and  thoracic  shield  dark 
brown  or  black.  The  most  satisfactory  means  of  control  is  directed 
against  the  eggs,  and  consists  in  the  use  of  a  miscible  oil  or  crude 
oil  spray  (Formula  18)  during  the  winter.  Great  care  must  be 
taken  to  thoroughly  drench  the  limbs  and  particularly  the  tops  and 
outside  branches.  Some  relief  may  be  had  during  the  summer  by 
spraying  with  2  pounds  of  powdered  or  4  pounds  of  paste  basic 
arsenate  of  lead  to  100  gallons  of  water. 

Green  and  Rosy  Apple  Aphis,  Aphis  pomi  DeGeer  and  Anura- 
phis  roseus  Baker. — Both  of  these  aphids  are  easily  distinguished  by 
their  color  and  the  characteristic  curling  of  the  leaves  caused  by 
their  method  of  attack.  Control  measures  are  difficult  and  must  be 
thorough  to  secure  satisfactorj'  results.  Late  dormant  lime-sulfur, 
1-10,  applied  just  before  the  buds  open,  gives  fair  results  in  killing 
the  eggs,  but  it  is  better  to  spray  from  the  time  of  the  bursting  of 
the  buds  until  the  leaf  buds  are  one-half  inch  long  with  nicotine 
and  soap  (Formula  27),  or  with  nicotine  and  distillate  emulsion  or 
miscible  oil  (Formula  24),  or  to  dust  thoroughly  with  5  or  6  per 
cent  nicodust.  At  this  time  the  young  stem-mothers  may  be  de- 
stroyed as  they  hatch  from  the  eggs. 


6  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Red  Humped  Caterpillar. — See  ' '  Prune. ' ' 

San  Jose  Scale,  Aspidiotus  perniciosus  Comst. ;  Oyster  Shell  Scale, 
Lepidosaphes  ulmi  (Linn.) ;  and  Other  Scale  Insects.— The  scales  of 
the  first  are  circular  and  gray,  while  those  of  the  second  are  oyster- 
shaped  and  similar  in  color.  They  occur  on  all  parts  of  the  tree,  the 
first  causing  a  red  or  purplish  stain  on  the  bark  and  fruit.  For  the 
San  Jose  scale  alone,  spray  with  lime-sulfur,  1-10,  during  the  winter 
months.  For  a  mixed  infection  of  scales,  spray  preferably  with  crude 
oil  emulsion  (Formula  18),  or  with  distillate  emulsion  (Formulas 
21-23),  or  with  miscible  oil.  The  lighter  oil  sprays  are  not  so  effi- 
cient as  the  crude  oil  emulsion. 

Tent  Caterpillars  and  Cankerworms. — See  "General  Subjects.'' 

Tussock  Moths,  Hemerocampa  vetusta  (Boisd.)  and  Notolophus 
aniiqua  (Linn.). — The  caterpillars  are  brilliantly  colored  and  clothed 
with  tufts  of  white  hair  on  the  dorsum,  with  a  single  long  black  tuft 
at  the  rear  and  two  in  front,  the  latter  being  responsible  for  the 
name  "horn  worms."  The  eggs  appear  as  white  flat  felty  masses 
on  the  old  cocoons  and  on  the  limbs  of  the  trees.  They  are  deposited 
in  late  summer  and  fall,  but  do  not  hatch  until  the  following  spring. 
The  female  moths  are  wingless,  while  the  males  are  normally  winged. 
Control  by  removing  the  egg  masses  during  the  winter  months.  Great 
numbers  of  the  caterpillars  may  be  jarred  from  the  trees  and  their 
reascending  prevented  by  applying  a  band  of  cotton,  wire  screen,  or 
tanglefoot  around  the  trunks.     Poison  sprays  are  of  little  use. 

Woolly  Apple  Aphis,  Eriosoma  lanigera  (Hausm.). — Easily  dis- 
tinguished by  the  reddish  bodies  completely  covered  with  white 
woolly  wax.  During  the  winter  months  spray  with  distillate  emul- 
sion (Formula  23),  miscible  oil,  or  carbolic  acid  and  distillate  emul- 
sion (Formula  26a).  For  the  root  form,  expose  the  crown  of  the 
roots  and  pour  in  4  or  5  gallons  of  any  of  the  above  spray  mixtures 
and  recover  the  roots.  Nicotine  sulfate  (Formula  27)  is  also  effec- 
tive, or  refuse  tobacco  stems  or  leaves  may  be  buried  in  the  soil  over 
the  main  roots  during  the  rainy  season.  Use  para-dichlorobenzene  dur- 
ing the  fall.  Delicious  and  Northern  Spy  rootstocks  are  somewhat 
immune  and  are  often  used  to  repel  serious  attacks  of  this  pest.  Of 
the  two  stocks  the  former  is  more  vigorous  and  easily  grafted. 

Combined  Spraying 

1.  For  serious  infestations  of  scale  insects,  for  removal  of  moss  or 
lichens,  and  for  a  general  clean-up,  use  lime-sulfur  1-10  or  crude  oil 
emulsion  (Formula  18)   during  the  winter. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  7 

2.  For  green,  rosy,  and  woolly  aphis,  use  distillate  emulsion  (Form- 
ula 23)  or  miscible  oils  just  as  the  buds  are  beginning  to  open.  If 
only  the  first  two  are  present  and  scab  is  a  serious  pest,  substitute 
late  dormant  lime-sulfur  1-10.  This  will  assist  in  the  control  of  the 
San  Jose  scale,  if  present.  Combinations  of  oil  sprays  for  insects 
with  lime-sulfur  or  Bordeaux  mixture  for  fungous  diseases  are  not 
considered  advisable. 

3.  For  codling  moth  and  scab  use  2  pounds  powdered  or  4  pounds 
paste  basic  arsenate  of  lead  to  100  gallons  of  1-35  lime-sulfur  when 
petals  are  falling.  For  mildew,  add  8  pounds  of  sulfur  paste  to  each 
100  gallons  of  the  above  and  one-half  pint  of  40  per  cent  nicotine 
sulfate  for  green  or  rosy  aphis.  For  later  infestations  of  codling 
moth  and  scab,  repeat  above,  following  recommendations  for  mildew 
and  aphis  if  these  need  attention. 

In  large  apple-growing  districts  obtain  advice  of  local  horticul- 
tural authorities  for  modifications  of  the  above. 

4.  For  summer  infestations  of  aphis  and  red  spiders,  a  combined 
nicotine  and  sulfur  dust  may  be  applied  to  great  advantage. 

APRICOT 

Armillaria,  Crown  Gall,  Sour  Sap,  Wood  Decay. — See  "  General 
Subjects,"  p.  53. 

Bacterial  Gummosis,  Bacterium  cerasi  Griffin. — Active  during 
moist  weather  of  winter  and  spring.  Attacks  buds,  twigs,  branches, 
trunks,  and  succulent  young  shoots.  On  the  last  there  is  a  killing 
and  blackening  of  tissue,  at  first  superficial  but  often  killing  the  shoot. 
Copious  turbid  or  colored  gum  appears.  Affected  bark  when  cut 
into  shows  moist  gumming  rot.  Cut  out  diseased  bark  and  disinfect 
wounds  and  tools  as  for  pear  blight.  (See  "Pear").  After  the 
first  rains,  the  orchard  should  be  frequently  inspected  and  all  cankers 
treated  promptly  to  stop  their  spreading.  Summer  treatment  is 
of  doubtful  value  in  controlling  the  trouble,  but  trees  should  be 
repaired  to  prevent  wood  decay.  (See  "General  Subjects,"  p.  58.) 
Appears  to  be  increasing  in  severity.  No  remedy  is  known  for  the 
phases  on  buds,  twigs  and  succulent  growth  in  early  spring.  A  heavy 
Bordeaux  spray  before  the  rains  begin  as  for  peach  blight,  may 
help. 

Black  Heart. — Certain  branches  die  back  suddenly  in  summer 
with  leaves  attached  and  the  wood  of  affected  twigs  becomes  dark- 
streaked  far  back  into  the  tree.     Peaches,  prunes,  and  almonds  are 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

sometimes  affected.  Avoid  excessive  irrigation,  severe  cutting  back, 
or  otherwise  promoting  too  succulent  growth.  Make  conditions  as 
normal  as  possible ;  trees  usually  outgrow  the  trouble.  A  publication 
on  this  subject  is  soon  to  appear. 

Brown  Rot,  or  Monilia  Brown  Rot,  Monilia  Blossom  Blight,  Gum- 
ming Twig  Blight  and  Monilia  Rot  of  Ripe  Fruit,  Sclerotinia  cine- 
rea  (Bon.)  Schrot.  {Sclerotinia  fructigena  or  Monilia  fructingena 
in  earlier  works  in  America). — The  brown  rot  fungus  is  active  only 
in  moist  weather,  but  may  then  be  very  destructive.  Flowers  are 
susceptible  when  the  white  petals  show  in  the  buds  and  remain  so  until 
the  ''jackets"  (calyxes  and  other  flower  parts)  are  shed  from  the 
fruit.  The  fungus  grows  down  through  the  flower  or  fruit,  caus- 
ing it  to  rot,  usually  without  falling,  and  penetrates  into  the  spur 
or  twig  for  several  inches.  Inner  bark  and  wood  turn  brown  and 
copious  amber  gum  appears.  Long  shoots  may  be  killed  by  girdling 
from  a  spur.  Ripening  fruit  is  attacked  (usually  in  injuries)  and 
rots,  becoming  covered  with  dusty  gray  powder.  If  allowed  to  dry 
out  the  rotted  fruit  becomes  a  tough  "mummy,"  often  hanging  in 
the  tree  over  winter.  Where  fruits  are  crowded,  whole  clusters 
frequently  are  lost. 

The  fungus  remains  alive  in  mummies  and  dead  twigs  and  forms 
spores  during  wet  weather  of  winter  and  spring.  All  stone  fruits 
and  almonds  are  attacked.     The  Madeline  pear  is  very  susceptible. 

After  the  crop  is  off,  or  at  any  time  during  fall  or  winter,  remove 
all  mummies  and  dead  twigs  and  plow  them  under,  bury  deeply  or 
burn.  Where  the  disease  is  serious,  spray  with  Bordeaux  8-8-50  in 
the  red  bud  stage  (just  before  the  white  petals  show).  Or  if  very 
bad  spray  several  times  in  quick  succession,  continuing  up  to  full 
bloom.  For  the  fruit  rot  Bordeaux  4-5-50  may  be  used  up  to  the 
time  when  it  will  remain  and  be  unsightly  on  the  fruit — perhaps  two 
months  before  ripening.  Lime  sulfur  is  efficient  in  case  of  brown 
rot,  but  has  frequently  caused  "sulphur  sickness'  in  apricot  trees, 
and  is  not  recommended.  Sulfur  sickness  has  appeared  as  yellowing 
of  foliage,  stunting  of  fruit,  and  failure  of  trees  to  bloom  normally 
the  following  year. 

Bud  Blight,  Shot  Hole,  Fruit  Spot,  Peach  Blight,  Coryneum  oeije- 
rinckii  Oud. — Buds  are  blackened  and  killed  during  winter;  spots 
killed  in  the  opening  leaves  fall  out  and  leave  holes,  and  small  red 
spots  with  light  centers  are  formed  in  the  young  fruit.  Spray  with 
Bordeaux  or  lime-sulfur  between  November  15  and  December  15,  and 
repeat  in  spring  when  buds  are  showing  pink.  See  "Almond"  and 
"Peach."     Destructive  in  interior  valleys  and  foothills. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  9 

Frost  Scabs,  Fruit  Cracking  and  Red  Specking,  Failure  of  Flower 
Buds  to  Open  on  Strong  Shoots,  Unfruitfulness  of  Some  Varieties. — 

Due  to  climate  or  obscure  causes,  and  often  confused  with  fungus 
diseases. 

Green  Rot  and  Twig  Blight,  Sclerotinia  libertiana  Fcl. — Often 
associated  with  brown  rot  and  confused  with  it.  Where  the  fungus 
shows  on  the  surface  it  is  snow  white  instead  of  gray  as  in  brown 
rot,  and  sclerotia  may  sometimes  be  found.  (See  "Stem  Rot"  of 
"Alfalfa,"  "Lemon  Rot,"  etc.).  Does  not  affect  the  ripening  fruit. 
Control  is  not  developed,  but  sprays  for  brown  rot  should  be  of  some 
value. 

RUST,  Transchelia  punctata  (Pers.)  Arth.  =  Puccinia  pruni. — 
Sometimes  causes  small  hard  points  in  the  skin  of  the  fruit,  resem- 
bling "fruit  spot"  above.  Also  rarely  there  has  been  severe  drop- 
ping of  young  leaves  in  early  summer  following  very  heavy  infection. 
Early  infection  apparently  came  from  old  rusted  leaves  which  hung 
on  the  trees  over  winter.  If  this  trouble  should  persist,  it  would 
probably  be  desirable  to  bring  down  the  old  leaves  during  winter  by 
means  of  a  caustic  spray  or  otherwise.  See  "Almond,"  "Peach," 
"Plum." 

Scab,  Cladosporium  carpophylum  Thum. — Sooty  patches  to  one- 
half  inch  in  diameter  and  often  confluent  form  on  the  fruit,  causing 
drying  and  cracking.  Sprays  for  brown  rot  will  probably  control  this, 
but  if  not  effective,  additional  sprays  after  full  bloom  should  be  tried, 
using  Bordeaux  (Formula  9,  p.  74). 

Branch  and  Twig  Borer,  Polycaon  confertus  Lee. — A  small  elong- 
ated brown  beetle,  one-quarter  of  an  inch  long,  which  bores  clean 
round  holes  at  the  bases  of  buds,  fruit  spurs,  and  in  the  forks  of  small 
twigs.  Often  makes  severe  pruning  necessary.  The  insect  breeds  in 
dead  oaks  and  prunings  of  fruit  and  other  trees.  Clean  up  and  burn 
dead  brush  and  prunings  around  orchards. 

Brown  Apricot  Scale,  Lecanium  corni  Bouche,  and  Black  Scale, 
Saissetia  oleae  (Bern.). — Immature  scales  of  both  species  are  brown 
or  grayish,  the  latter  having  a  distinct  "H"  on  the  back.  They 
mature  in  May  and  June  and  are  nearly  hemispherical;  the  former 
is  smooth  and  brown  and  the  latter  black.  Control  is  directed  against 
the  immature  winter  forms  which  occur  on  the  new  growth.  Spray 
the  trees  when  dormant,  December  to  February,  with  crude  oil  emul- 
sion (Formula  18),  distillate  emulsions  (Formulas  20-23),  and  mis- 
cible  oils,  all  of  which  give  excellent  control  for  both  of  these  scales. 
Thoroughness  of  application  is  necessary.  (See  Circular  No.  224, 
Calif.  Agr.  Exp.  Sta.,  Univ.  Calif.,  Dec,  1920.) 


10  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

California  Peach  Borer. — See  "Peach." 

Cankerworms. — See  "General  Subjects." 

Fruit  Tree  Leaf  Roller.— See  "Apple." 

Peach  Twig  Borer.— See  "Peach." 

Red  Humped  Caterpillar. — See  "Prune." 

Shot  Hole  Borer,  Xyleborus  xylographies  Say  and  Bark  Beetle, 
Eccoptog aster  rugulosus  (Ratz.). — Very  small  beetles  boring  into  the 
sapwood  and  heartwood  of  various  fruit  trees,  preferring  usually 
those  not  in  the  best  of  health.  White  larvae  of  the  latter  may  be 
found  during  the  winter  months  in  sapwood,  where  they  may  en- 
tirely girdle  the  trees.  Keep  the  trees  growing  vigorously;  prune 
out  and  burn  all  dead  wood;  destroy  all  infested  branches  imme- 
diately. 

Combined  Spraying 

Lime  sulfur  1  to  10,  applied  as  the  buds  are  beginning  to  open, 
will  control  peach  twig  borer,  remove  moss  and  give  the  trees  a  gen- 
eral clean  up,  but  this  may  cause  sulfur  sickness.  (See  "Brown 
Rot.")  General  clean  up  may  be  accomplished  by  a  dormant  spray 
of  crude  oil  emulsion  (Formula  18,  p.  82)  or  miscible  oil  (p.  85),  and 
peach  twig  borer  may  be  controlled  by  adding  basic  arsenate  of 
lead  powder,  3  lbs.  to  200  gals,  of  Bordeaux  mixture,  in  spring,  to 
control  broAvn  rot  or  bud  blight  and  fruit  spot.  See  also  "Twig 
Borer ' '   under    ' '  Peach. ' ' 

ARTICHOKE 

Artichoke  Plume  Moth,  Platyptilia  carduidactxjla  (Riley). — This 
moth  is  brown  with  narrow  wings  and  one  inch  long.  The  caterpillars 
are  less  than  one  inch  long,  yellowish  with  black  heads.  They  feed 
chiefly  upon  the  developing  heads  of  the  artichoke,  making  deep 
tunnels  or  eating  through  the  bracts.  Their  work  is  often  very  destruc- 
tive and  considerable  loss  occurs  every  spring  because  of  it. 

Field  sanitation  is  one  of  the  best  means  of  control.  Infested 
heads  should  be  removed  at  every  picking  and  burned.  Burning  or 
deep  plowing  should  be  practiced  to  dispose  of  the  old  plants  after 
cutting  in  May  and  June.  Thistles  and  deserted  or  wild  artichoke 
plants  should  be  promptly  destroyed  to  eliminate  breeding  places. 
Dusting  with  5  per  cent  nicodust  or  with  a  combination  of  5  per 
cent  nicodust  to  which  1  pound  of  powdered  arsenate  of  lead  is 
added  to  every  4  pounds  of  the  nicodust  is  recommended  after  each 
picking,  until  the  attacks  are  reduced  to  a  minimum. 


Circular  265]  plant  disease  and  pest  control  11 

Artichoke  Aphis,  Myzus  braggii  Gill. — A  green  and  black  aphis 
©ften  in  immense  numbers  on  the  heads  and  the  undersides  of  the 
leaves.  Dust  with  5  per  cent  nicodust  or  spray  with  nicotine,  sulfate 
and  soap   (Formula  27.) 

ASPARAGUS 

Rust,  Puccinia  asparagi  D.  C. — Minute  yellowish  blisters  or  sori 
appear  on  leaves  and  stems;  these  rupture  and  become  rust-colored 
and  dusty  and  later  black.  Plants  become  pale  and  bare  and  are 
much  weakened  for  succeeding  crops.  Keep  down  all  volunteer 
growth  in  and  about  the  fields.  Burn  all  old  growth  after  it  dies 
down  and  cultivate  all  surfaces  well  before  new  growth  comes  up. 
After  cutting  stops,  irrigate  and  cultivate  to  secure  vigorous  growth, 
and  in  about  three  weeks  dust  with  sulfur  while  the  dew  is  on,  or 
spray  with  resin-Bordeaux  (Formula  10a,  p.  75)  or  lime-sulfur 
containing  fish-oil  soap  for  a  spreader,  or  with  fish-oil  soap  followed 
by  dusting  with  sulfur  while  still  wet.  Repeat  once  or  twice,  accord- 
ing to  the  severity  of  the  disease  in  the  vicinity.  For  young  fields, 
dust  repeatedly  with  sulfur  as  above  to  prevent  infection,  beginning 
when  the  tops  first  fully  feather  out. 

Asparagus  Beetle,  Crioceris  asparagi  Linn. — The  beetles  are  slen- 
der, one-fourth  of  an  inch  long,  metallic  blue-black  with  red  and 
yellow  markings.  The  larvae  are  dull  brown  or  olive  green  with 
black  head  and  legs.  They  feed  in  great  numbers  upon  the  seed- 
lings. Control  by  clean  culture,  by  cutting  and  burning  seedlings, 
or  by  spraying  them  with  nicotine  soap  spray  (Formula  24  or  27.) 
A  6  per  cent  nicodust  also  gives  quite  efficient  control. 

Garden  Centipede,  Scutigerella  calif  arnica  (Woodw.). — These  are 
small,  white,  centipede-like  animals,  scarcely  more  than  one-quarter 
of  an  inch  long.  They  live  in  the  damp  soil  in  great  numbers  and 
often  seriously  damage  the  young  asparagus  tips  before  they  reach 
the  surface  of  the  soil.  Clean  culture,  winter  flooding,  and  crop 
rotation  are  the  best  control  suggestions. 

AVOCADO 

Pythiacystis  Canker,  Pythiacystis  citrophthora  S.  &  S. — Limb  and 
trunk  cankers,  resembling  gummosis  of  lemon,  but  the  gummy  exu- 
date hardens  into  a  granular  whitish  mass.  Treat  as  for  citrus  gum- 
mosis.   See  ("Citrus  Fruits"). 


12  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Soil  or  Water  Injury. — Certain  sickly  conditions  apparently 
caused  by  uneven  moisture  due  to  hardpan  or  other  soil  defects. 
Trees  apparently  are  sensitive  to  waterlogging  of  soil  and  have  poor 
recuperative  power  after  such  injury. 

Branch  and  Twig  Borer. — See  "Apricot."  Sap  collecting  in  the 
burrows  produces,  on  evaporation,  white  powdery  masses  over  the 
entrances,  completely  concealing  them. 

Fruit  Tree  Bark  Beetle.— See  "Apricot." 

Spanish  Red  Scale,  Chrysomphalus  dictyospermi  Morgan. — A  pale 
brown,  circular  scale,  infesting  all  parts  of  the  tree  and  serious  in 
greenhouses,  but  as  yet  not  adapted  to  orchard  conditions.  Control 
by  fumigation  with  hydrocyanic  acid  gas. 

Thrips :  Bean  Thrips,  Heliothrips  fasciatus  Perg.,  and  Greenhouse 
Thrips,  Heliothrips  haemorrhoidalis  Bouche. — See  "Prune."  These 
insects  attack  the  leaves  and  fruit,  causing  a  shiny,  hard  discolored 
surface  which  has  a  tendency  to  check,  or  crack,  and  which  is  covered 
with  numerous  fine  specks  of  excrement. 

BARLEY— See  "Grain" 

BEAN 

Anthracnose,  Collet otrichum  lindemuthianum  (S.  &  M.)  B.  &  C. — 
Spots  on  leaves,  stems,  and  pods,  up  to  two-fifths  inch  in  diameter, 
dark-colored,  usually  with  a  red  border  and  pinkish  in  the  center. 
Very  rare  and  unimportant  in  California. 

Mildew,  Erysiphe  polygoni  D.  C. — Forms  a  powdery  white  cover- 
ing over  green  parts  of  the  plants;  later  brownish.  May  seriously 
reduce  the  vitality  of  the  plants.  Dust  with  sulfur  at  first  appear- 
ance, or  with  sulfur  nicodust  if  thrips  or  aphis  are  present.  Some- 
times appears  late  where  the  pods  are  well  formed.  No  treatment 
is  necessary  in  that  case. 

Rust,  Uromyces  appendiculatus  (Pers.)  Link. — Rust-colored  spore 
masses  or  sori  of  pinhead  size  break  through  the  lower  surface  of 
the  leaf,  with  yellow  spots  above.  Affected  leaves  are  weakened  and 
production  decreases.  Dust  with  sulfur  at  first  sign  of  the  disease 
and  keep  the  surface  of  the  soil  dry  by  cultivation.  Resistant  varieties 
have  been  reported. 

Wilt  or  Stem  Rot,  Corticium  vagum  B.  &  C=Rhizoctonia,  and 
Fusarium  sp. — Many  plants  die  while  small  from  rot  near  the  surface 
of  the  soil,  while  others  wilt  at  different  stages.  Prepare  the  soil 
very  thoroughly,  plant  as  late  as  possible,  avoiding  cold  and  wet 
weather.     Save  seed  from  strong,  well-matured  plants. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  13 

Bean  Aphis,  Aphis  rumicis  Linn. — A  small  black  louse  collecting 
in  great  numbers  on  the  leaves  and  tender  tips.  Use  5  per  cent 
nicodust  or  spray  with  nicotine  paste  spray  (Formula  27a). 

Bean  Thrips,  Heliothrips  fasciatus  Perg. — A  small  dark  thrips 
with  black  and  white  wings.  The  larvae  are  white  and  pinkish 
and  appear  in  great  numbers  on  the  lower  surface  of  the  leaves. 
Treatment  the  same  as  for  bean  aphis. 

Bean  Weevil,  Acanthoscelides  obtectus  Say. — The  adults  are  short, 
robust,  and  about  one-eighth  inch  long.  The  color  varies  from  gray 
to  brown  with  pale  spots  on  the  dorsum.  The  larvae  work  within 
the  stored  beans,  from  which  the  adults  emerge  through  round  holes. 
Breeding  continues  in  storage.  Fumigate  in  storage  with  carbon 
bisulfid,  10  to  30  pounds  to  every  1000  cubic  feet  of  air  space,  the 
amount  depending  upon  the  tightness  of  the  container.  The  temper- 
ature should  be  above  70°  F.  to  secure  satisfactory  control  by  killing 
eggs,  larvae,  and  adults. 

Garden  Nematode. — See  "General  Subjects."  Black  eyes  and 
Teparies  are  more  resistant  than  other  beans,  but  are  sometimes 
badly   infested. 

Red  Spider  or  Two-Spotted  Mite,  Tetranychus  telarius  Linn. — A 
very  small  yellow,  pale  green  or  reddish  mite,  often  with  two  large, 
or  six  small,  dark  spots  on  the  body.  Feeds  on  the  under  side  of 
leaves  and  often  spins  a  considerable  web.  If  possible  keep  the 
beans  well  irrigated  and  cultivated  and  in  good  healthy  condition. 
Begin  sulfuring  as  soon  as  the  mites  appear  and  continue  throughout 
the  summer,  using  90  parts  of  dry  sulfur  to  10  parts  of  finely  ground 
dry  hydrated  lime. 

Wireworms. — See  "General  Subjects." 

BEET 

Curly-leaf  =,  Curly-top  or  Blight. — Transmitted  by  the  beet  leaf 
hopper,  Eutettix  tenella  Baker.  Leaf  margins  curl  inward  or  rarely 
outward  and  are  much  dwarfed  and  deformed;  plants  are  stunted 
and  easily  killed  by  drought  and  heat;  young  leaves  show  trans- 
parent venation  (a  clearing  of  the  ultimate  leaf  vein  branches),  and  a 
warty  condition  usually  develops  on  the  backs  of  veins  on  old  leaves. 
Roots  often  become  hairy  and  show  dark  rings  in  cross-section.  In 
the  cool  districts  subject  to  ocean  fogs,  the  insects  do  not  reproduce 
abundantly  and  the  disease  when  established  is  less  injurious.  Beets 
in  all  other  parts  of  the  Pacific  slope  and  of  the  Rocky  Mountains 
are  liable  to  injury,  but  in  certain  regions  have  been  observed  to 


14  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

suffer  less  than  in  others.  Early  planting  to  bring  the  beet  to 
a  good  size  before  the  spring  invasion  of  the  insects  from  plains 
and  foothills  is  generally  successful  except  in  years  following  early 
fall  rains,  which  bring  up  filaree  and  other  vegetation  and  cause  a 
large  number  of  insects  to  winter  in  the  cultivated  area.  Blighted 
' '  stechlings ' '  do  not  produce  seed  successfully,  although  the  symptoms 
may  not   always  be   apparent. 

The  sugar  beet  leafhopper,  Eutettix  tenella  Baker,  referred  to 
above  is  wingless  in  the  immature  form  and  winged  when  full  grown. 
The  adults  average  about  one-fourth  inch  in  length.  The  color  varies 
with  the  season;  those  of  the  spring  brood  being  pale  green;  those 
of  the  summer  brood  cream  colored;  while  the  winter  generations 
are  dark  colored  with  darker  markings  on  the  wing  covers.  The 
insects  are  to  be  found  chiefly  on  the  under  surfaces  of  the  leaves  or 
between  the  stems  near  the  crown,  thus  producing  the  characteristic 
' '  curly-leaf ' '  described  above. 

Downy  Mildew,  Peronospora  schactii  Fcl. — Inner  leaves  become 
curled,  dwarfed,  and  covered  below  with  a  violet  mildew.  Develops 
in  moist  weather.     Remove  affected  plants  and  destroy. 

Leaf  Spot,  Cercospora  beticola  Sacc. — Leaves  have  dead  gray  spots, 
mostly  one-sixteenth  inch  in  diameter  or  smaller  with  borders  of 
brown  or  purple.     Treatment  not  considered  necessary. 

Rust,  Uromyces  betae  (Pers.)  Kuhn. — Powdery  dark  brown  pus- 
tules of  pinhead  size  appear  on  the  green  leaves.     Not  serious. 

Seedling  Root  Rot,  Corticium  vagum  B.  &  C=Rhizoctonia,  and 
Fusarium  sp. — Roots  are  injured  and  become  misshapen  and  forked; 
plants  are  delayed  or  stunted  or  die.  Make  the  soil  conditions  as 
favorable  as  possible  for  vigorous  growth.  Replant  if  the  stand  is 
too  thin. 

Armyworms  and  Cutworms. — See  "General  Subjects.' ' 

Beet  or  Spinach  Leaf -miner. — See  ' '  Spinach. ' ' 

Grasshoppers. — See  ' '  General  Subjects. ' ' 

Nematodes. — See  "General  Subjects."  The  beet  is  attacked  by 
two  species,  the  garden  nematode,  Heterodera  radicicola  Greef,  which 
produces  galls  on  a  number  of  plants,  and  the  beet  nematode,  H. 
schachtii  Schmidt,  which  is  confined  to  sugar  beets  and  does  not 
produce  galls. 

Wireworms. — See  "General  Subjects,"  For  the  sugar  beet  wire- 
worm,  Limonms  calif ornicus  (Mann.),  plow  in  fall  to  destroy  the 
pupae.  Plant  early  and  practice  clean  culture.  Trap  the  adults 
by  means  of  piles  of  straw  and  burn  in  late  fall  or  winter. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  15 

BUSH  FRUITS  (Blackberry,  Loganberry,  Raspberry) 

Bluestem,  Verticillium  caulophagus  (Law.) — Blackcaps  and  vari- 
ety Ranare  are  said  to  be  particularly  susceptible.  Plants  become 
sickly  and  canes  die  back;  longitudinal  dark  streaks  appear  in  the 
wood  when  the  stems  are  cut  across.  Control  not  developed.  Select 
plants  from  healthy  fields. 

Cane  Blight,  Leptosphaeria  coniothyrium  Sacc,  =  Coniothyrium. 
— Dead  areas  appear  on  the  canes,  which  are  often  girdled  and  killed. 
Cut  out  and  burn  all  affected  parts  in  the  fall.  Spray  with  Bor- 
deaux during  the  dormant  season.  Sometimes  confused  with  anthrac- 
nose,  which  we  have  not  recognized  in  California. 

If  foliage  and  cane  diseases  are  serious,  there  will  probably  be 
an  advantage  in  removing  the  fruiting  canes  immediately  after  the 
crop  is  off,  or  at  least  before  any  moist  autumn  weather.  Spray 
during  the  dormant  season  with  lime  sulfur  1-10  or  Bordeaux 
(Formula  9,  p.  74).  Give  proper  irrigation  and  cultivation.  If 
fields  become  unhealthy,  reset  in  new  land,  using  healthy  plants. 

Crown  Gall,  Bacterium  tumefaciens  Sm.  &  T. — See  "General  Sub- 
jects." 

Fruit  Mold,  Botrytis  and  Other  Fungi. — Avoid  mixing  bruised  or 
moldy  berries  with  good  ones. 

Leaf  Spot,  Septoria  rubi  West. — Small  dead  spots  on  leaves  and 
canes  with  brown  or  reddish  borders.  Liable  to  be  severe  on  the 
variety  mammoth  and  on  wild  dewberry.  Treat  as  for  cane  blight 
above. 

Orange  Rust,  Gymnoconia  interstitialis  (Schlect.)  Lagerh. — Indi- 
vidual plants  are  affected  and  ruined.  New  shoots  come  up  pale, 
dwarfed  and  with  the  leaves  curved  inward  and  drawn  upward.  The 
surface  of  the  leaves  becomes  covered  with  orange  colored  spores. 
Dig  out  and  burn  affected  plants  at  the  first  appearance  of  the  dis- 
ease. Spray  healthy  plants  in  the  vicinity  with  Bordeaux  mixture 
to  prevent  infection. 

Raspberry  Horntail,  Hartigia  cressoni  (Kirby). — The  small  white 
larvae  are  shaped  somewhat  like  the  letter  ' '  S ' '  and  when  mature  are 
nearly  one  inch  long.  They  first  attack  the  tender  tips  of  the  new 
canes  and  after  girdling  them  and  causing  wilting  they  work  down 
the  pith  to  the  roots,  where  they  spend  the  winter.  Cut  off  the  young 
tips  as  soon  as  wilting  is  noticed  so  as  to  kill  the  larvae  before  they 
reach  the  roots.  Remove  all  dead  canes  in  winter,  using  care  to  dig 
out  the  borers  at  that  time. 


16  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Rose  Scale,  Aulacaspis  rosae  (Bouche). — A  pure  white  scale 
often  found  in  great  numbers  at  the  bases  of  the  old  canes.  Spray  in 
winter  with  distillate  emulsion  (Formula  23)  or  with  miscible  oil. 
Prune  out  old  canes  every  year,  because  infestation  spreads  from  them. 
Serious  only  where  pruning  is  not  practiced  every  year.  Lime-sulfur 
used  as  a  fungicide  gives  some  control. 

The  Blackberry  Mite,  Eriophyes  gracilis  (Nalepa). — This  is  a  small 
microscopic  mite  causing  the  red-berry  condition  of  the  Himalaya 
blackberry  throughout  the  state.  The  mites  attack  the  drupelets  of 
the  berries  shortly  after  the  flowers  open  and  continue  to  work  in 
the  fruit,  preventing  ripening.  The  winter  is  spent  in  the  buds  and 
the  pest  can  be  effectually  controlled  by  spraying  the  infested  vines 
in  the  early  spring,  in  February  or  March,  as  the  leaf  buds  are 
opening,  with  lime-sulfur  solution,  4  gallons  to  100  gallons  of  water. 

Summer  control  may  be  obtained  by  spraying  with  5  pounds  of 
wettable  sulfur  to  100  gallons  of  water. 

CABBAGE 

Yellows,  Wilt,  Fusarium  conglutinans  Woll.  —  Plants  gradually 
turn  yellow  with  falling  of  lower  leaves.  Stem  shows  dark  ring  when 
cut  across.  Loss  may  be  severe.  Reported  as  especially  trouble- 
some on  kale.  Grow  plants  in  soil  free  from  disease.  (See  "soil 
disinfection,"  p.  95.)  Avoid  infected  land.  Certain  strains  of 
cabbage  are  resistant. 

Armyworm  and  Cutworms. — See  "General  Subjects."  Scatter 
poison  bran  (Formula  4)  broadcast  over  the  ground  and  plants  in  the 
evening. 

Cabbage  Aphis,  Aphis  brassicae  Linn. — A  small  green  aphis  en- 
tirely covered  with  fine  whitish  powdery  wax.  Is  best  controlled  by 
liberal  and  repeated  applications  of  nicotine-distillate  spray  (Formula 
24)  or  of  nicotine  soap  (Formula  27).  Nicodust  gives  only  partial 
control. 

Cabbage  Worm,  Pontia  rapae  (Linn.). — A  small  green,  velvety 
worm,  one  inch  long  when  mature,  which  feeds  upon  the  leaves  and 
destroys  the  heads.  The  adults  are  white  butterflies  with  dark 
spots  on  the  front  wings.  Young  cabbage  plants  may  be  protected  by 
using  arsenate  of  lead,  1  pound  of  powder  or  2  pounds  of  paste,  to 
50  gallons  of  water.  This  should  not  be  applied  after  the  heads  are 
formed  because  of  possible  poisoning  of  humans.  Later  control  may 
be  accomplished  by  applying  a  nicotine  soap  spray  (Formula  27). 
A  5  per  cent  nicodust  also  gives  very  good  control  when  liberally 
applied. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  17 

Cabbage  Root  Maggot,  Phorbia  brassicae  Bouche. — The  small  white 
maggots,  one-fourth  inch  long,  are  found  tunneling  the  roots  which 
are  often  completely  destroyed  by  them.  The  insect  also  attacks 
radishes,  turnips,  cauliflower  and  other  related  plants.  The  most 
effective  means  of  control  is  in  the  use  of  a  repellent  composed  of 
1  ounce  of  corrosive  sublimate  to  10  gallons  of  water.  Three  appli- 
cations should  be  made,  using  one  cupful  (*/4  pint)  around  the  base 
of  each  plant,  as  follows:  1st  application  3  or  4  days  after  trans- 
planting ;  2nd  application  9  or  10  days  after  transplanting ;  3rd 
application  19  to  20  days  after  transplanting.  Later  applications 
should  not  be  made  on  account  of  the  danger  of  poisoning  the  plants 
for  market.  The  material  may  be  applied  with  a  watering  can  by 
regulating  the  flow.  Clean  up  all  refuse  in  the  fall  and  plow  and 
cultivate  thoroughly  during  fall,  winter  and  spring  before  trans- 
planting to  expose  and  kill  overwintering  pupae  in  the  soil. 

CAMELLIA 

Bud  Blight. — Browning  of  the  tips  of  the  buds,  followed  by 
their  decay  and  dropping,  due  frequently  to  injury  from  thrips. 
This  should  not  be  confused,  however,  with  the  dropping  of  the  buds 
caused  from  lack  of  irrigation. 

CANTALOUPE.     See  ' '  Melon. ' ' 

CASABA.     See  "Melon." 


CELERY 

Blight,  Cercospora  apii  Fr.  and  Septoria  petroselini  Desm. — Large 
or  small  dead  spots  appear  on  the  leaves  and  leaf  stalks,  especially 
after  cutting,  and  rapid  deterioration  follows.  Spray  repeatedly  with 
Bordeaux  (Formula  9),  especially  in  moist  weather,  commencing  in 
the  seed  bed. 

Aphids,  Rhopalosiphum  persicae  (Sulz.)  and  Siphocoryne  capreae 
(Fab.). — Green  aphids  attacking  the  stems  and  leaves  of  the  plants. 
Spray  with  nicotine  soap  (Formula  27)  or  dust  with  5  per  cent  nico- 
dust. 

Celery  Caterpillar,  Papilio  zolicaon  Boisd. — The  caterpillars  are 
beautifully  marked,  green,  black  and  orange,  and  feed  upon  the  leaves. 
Hand  pick  or  spray  with  arsenate  of  lead  not  later  than  three  weeks 
before  harvest  (Formula  2). 


18  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


CHERRY 

Armillaria,  Wood  Decay,  Sour  Sap. — See  ''General  Subjects." 
Gummosis,  Die-back. — See  "General  Subjects."  Several  distinct 
troubles  are  involved,  and  frequently  diagnosis  is  difficult.  On  cer- 
tain shallow  soils  it  is  reported  that  cherries  die  after  a  few  years  with 
copious  gumming  throughout  the  top.  For  bacterial  gummosis  it  is 
recommended  to  grow  Mazzard  seedlings  in  the  orchard  and  top  work 
after  several  years  with  the  desired  varieties  above  the  main  forks. 
(See  "Apricot.")  Cherries  are  sensitive  to  excess  of  water  in  the 
soil  and  to  summer  drought  and  do  not  recover  well  from  injury 
through  soil  defects. 

Leaf  and  Fruit  Spot,  Coryneum  heijerinckii  Oud. — See  "Apricot," 
"Peach,"  "Almond." 

Leaf  Curl,  Exoascus  cerasi  Fuckel. — Leaves  are  affected  in  a  way 
similar  to  peaches  with  peach  leaf  curl,  but  the  symptoms  less  pro- 
nounced. (See  "peach.")  The  treatment  for  peach  leaf  curl  has 
been  reported  by  practical  orchardists  to  be  successful  on  cherry. 
Rather  rare. 

Leaf  Spot,  Coccomyces  hiemalis  =  Cylindrosporium. — Tiny  spots 
covering  most  of  the  leaf  surface  and  becoming  fused  at  the  lower 
edge.  Under  side  shows  whitish  coating  of  spores.  Not  serious  as 
yet.  Controlled  in  the  East  by  Bordeaux  mixture,  5-5-50,  or  lime- 
sulfur  1-50,  adding  iron  sulfate  1%  pounds,  or  dusting  with  sulfur. 
Applications  as  follows:  (1)  when  the  fruit  is  free  from  the  calyx, 
(2)  two  weeks  later,  (3)  just  after  the  fruit  is  picked. 

Black  Cherry  Aphis,  Myzus  cerasi  Fabr. — A  shiny  black  aphid 
with  long  honey  tubes,  appearing  in  spring  and  early  summer  and 
causing  severe  curling  of  the  leaves.  Spray  with  nicotine  and  soap 
(Formula  27)  or  dust  thoroughly  with  5  per  cent  nicodust  as  soon 
as  aphids  appear. 

California  Peach  Borer. — See  "Peach." 

Cankerworms. — See  "General  Subjects." 

Cherry  Fruit  Sawfly,  Hoplocampa  cookei  (Clarke). — The  small 
white  larvae  work  within  the  partly  developed  fruits  of  the  cherry 
and  plum  and  are  at  times  responsible  for  much  damage.  Their 
presence  is  indicated  by  the  dropping  of  fruit  and  by  the  small  round 
exit  holes  in  fruits  which  are  hardly  half -grown.  The  best  treatment 
is  the  application  of  arsenate  of  lead  (Formula  2)  just  when  the  petals 
are  opening. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  19 

Cherry  Slug,  Caliroa  cerasi  (Linn.). — The  common  name  applies 
to  the  small  dark  green  or  blackish  slug-like  larvae  which  are  nearly 
one-half -inch  long  and  which  feed  upon  the  leaves  in  great  numbers 
almost  defoliating  the  trees  in  some  years.  Because  of  their  slimy 
covering  they  are  readily  killed  by  the  application  of  various  dusts, 
such  as  finely  ground  hydrated  lime,  ashes,  road  dusts,  etc.,  but  are 
best  controlled  by  the  applications  of  2  per  cent  or  5  per  cent  of  nico- 
dust.     The  regular  arsenate  of  lead  sprays  (Formula  2)  are  also  good. 

Pear  Thrips.— See  "Pear." 

Red  Humped  Caterpillar. — See  " Prune.' ' 

Tent  Caterpillars. — See  "General  Subjects." 

CHRYSANTHEMUM 

Rust,  Puccinia  chrysanthemi  Eoze. — Small  dark  pustules  or  sori 
appear  on  the  lower  side  of  leaves.  Fertilize  and  irrigate  freely  to 
produce  vigorous  plants. 

Aphids  (Various  Species). — Spray  with  nicotine  and  soap  (Form- 
ula 27)  or  dust  with  5  per  cent  nicodust  when  the  insects  appear. 

Chrysanthemum  Gall  Fly,  Diarthronomyia  hypogaea  (Low). — The 
small  yellowish  or  white  larvae  cause  numerous  pointed  galls  on  the 
leaves  and  stems  and  seriously  injure  the  terminal  buds.  Great  num- 
bers of  minute  slender  red  eggs  are  laid  on  the  plants  in  the  spring 
and  early  summer,  and  these  may  be  readily  killed  by  repeated  appli- 
cations of  nicotine  and  soap  (Formula  27).  Trim  the  plants  to  the 
ground  in  spring  to  eliminate  hold-over  forms. 

Chrysanthemum  Leaf  Miner,  Phytomyza  chrysanthemi  Kow. — 
The  injury  due  to  this  insect  consists  in  numerous  mines  on  the  upper 
side  of  the  leaves  just  under  the  epidermis.  These  are  made  by  the 
small  whitish  maggots,  which  are  easily  killed  within  their  burrows  by 
applying  one  part  of  40  per  cent  nicotine  sulfate  to  600  parts  of  water. 

CINERARIA 

Leaf  Miner. — Injury  similar  to  that  of  the  chrysanthemum  leaf 
miner  and  caused  by  the  same  insect. 

CITRUS  FRUITS  (Grapefruit,  Lemon,  Orange) 

Blast,  Black  Pit,  Bacterium  citriputeale  C.  0.  Smith. — Blast  occurs 
only  in  very  moist  seasons  and  districts;  black  pit  occurs  with  blast 
and  also,  rarely,  in  less  moist  localities.  Blast  is  a  watery  deteriora- 
tion of  leaves  and  petioles  extending  to  a  shield-shaped  area  in  the 


20  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

twig  about  the  base  of  the  leaf.  Leaves  die  and  dry  up  in  place,  the 
twig  lesions  turn  dark,  dry  up,  and  heal,  and  shed  off  in  two  or  three 
years.  Where  several  leaves  are  killed,  the  twig  may  be  much  weak- 
ened or  die.  Black  pit  consists  of  dark,  sunken  spots  in  the  rind 
of  the  fruit.  They  do  not  decay.  Grow  bushy,  compact  trees  and 
avoid  severe  pruning.  Protect  the  orchard  with  windbreaks  against 
prevailing  rain  storms.  For  northern  California  conditions,  spray 
from  October  to  December  with  Bordeaux  or  ammonia  copper  car- 
bonate; repeat  as  soon  as  the  fruit  is  off  or  before  January  1  with 
Bordeaux. 

Blue  Mold,  Green  Mold,  Penicillium  sps. — Rots  the  entire  fruit, 
starting  in  spots  and  becoming  a  powdery  blue  or  green,  and  gray. 
Avoid  even  minutest  injuries  in  picking  and  handling  fruit. 

Brown  Rot  of  Lemon  or  Pythiacystis  Rot,  Pythiacystis  citroph- 
thora,  S.  &  S. — See  also  "Gummosis."  This  disease  is  distinct  from 
brown  rot  of  apricots  or  monilia  rot.  A  rather  light  brown  rot  of 
fruit,  causing  only  slight  change  in  texture  at  first ;  develops  rapidly 
and  spreads  by  contact.  There  is  a  characteristic  odor  and  a  slight 
surface  mold  in  moist  atmosphere.  Develops  in  moist  weather.  When 
prevalent,  spray  the  lower  branches  and  ground  beneath  with  Bor- 
deaux mixture  (Formula  9).  Straw  mulch  also  is  useful.  Do  not 
allow  boxes  of  fruit  to  stand  over  night  in  the  orchard.  Use  blue- 
stone  in  the  wash  water  (Formula  12,  p.  75),  maintaining  a  constant 
strength  of  1%  lbs.  to  1000  gals.  Consult  your  farm  advisor  for 
special  methods  for  keeping  the  strength  of  solution  constant  where 
alkaline  water  is  used.  Grade  out  very  carefully  all  orchard  infected 
fruits  before  storing. 

Cottony  Rot,  Sclerotinia  libertiana  Fcl. — See  " Alfalfa,"  ''Apri- 
cot," etc.  A  serious  citrus  fruit  rot  in  storage  locally  after  wet 
weather.  A  snow  white  downy  mold  appears,  causing  a  soft  rot  which 
spreads  rapidly  by  contact.  Twigs  are  sometimes  killed.  Treat- 
ment as  for  brown  rot  of  lemon,  but  the  spores  are  much  more  resist- 
ant. See  the  farm  advisor  or  consult  the  University  of  California, 
College  of  Agriculture,  for  details  in  control. 

Damping  Off,  Armillaria  Root  Rot,  Wood  Decay. — See  "General 
Subjects,"  p.  53. 

Gummosis,  Phythiacistis  citrophthora  Smith  &  Smith. — Copious 
exudation  of  gum  on  the  lower  part  of  the  trunk.  The  bark  of  the 
affected  part  dies  and  the  diseased  area  may  continue  to  spread  until 
the  tree  is  girdled  and  killed.  Cut  out  all  affected  bark  as  soon  as  dis- 
covered and  treat  the  wounds  with  Bordeaux  paste    (Formula  10, 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  21 

p.  74).  Do  not  allow  water  to  stand  about  the  base  of  trees.  In 
planting  keep  the  point  of  budding  well  above  ground  and  never  allow 
the  soil  to  pile  up  around  the  trunk.  For  heavy  soil,  use  trees  high- 
budded  on  sour  orange  root.    See  also  " General  Subjects,"  p.  56. 

June  Drop. — Young  fruits  up  to  nearly  1  inch  in  diameter  turn 
pale  and  drop  off.  Especially  troublesome  with  navel  oranges  during 
severe  hot  periods.  Any  deficiency  in  vigor  of  the  tree  or  of  moisture 
supply  in  the  soil  will  presumably  make  the  trouble  worse.  Build  up 
the  vigor  of  the  trees;  secure  the  best  possible  moisture  condition  of 
the  soil ;  plant  windbreaks.  Consult  your  farm  advisor  or  local 
authorities. 

Mottled  Leaf. — Add  as  much  organic  matter  to  the  soil  as  possible 
in  the  form  of  green  manure  crops,  bean  straw,  and  manure.  Avoid 
continual  fertilization  with  nitrate  of  soda.  See  that  water  pene- 
trates to  the  subsoil  and  keeps  it  uniformly  moist.  See  "General 
Subjects,"  p.  57. 

Scaly  Bark. — Bark  at  first  becomes  roughened  in  a  small  area; 
roughening  spreads  and  deepens,  finally  gumming  heavily,  encircling 
the  trunk  or  limb  and  causing  its  death.  Scrape  off  all  visibly  affected 
bark,  leaving  the  inner  bark,  extending  2  or  3  inches  beyond  the 
edges  of  the  spot.  Cover  the  wounds  with  Bordeaux  paste  (Formula 
10)  or  other  suitable  fungicide.  Cut  off  badly  affected  branches. 
Watch  all  trees  very  closely  in  groves  where  the  disease  is  present 
and  eradicate  new  cases  at  first  appearance.  Do  not  use  Bordeaux 
if  the  trees  are  soon  to  be  fumigated. 

Aphids  (Various  Species). — Use  nicotine  and  soap  spray  (Formula 
27  or  a  5  per  cent  nicodust. 

Armyworms  and  Cutworms. — See  "General  Subjects." 

The  European  Red  Mite,  Paratetranychus  pilosus  C.  &  F.  and  the 
Two-Spotted  Mite,  Tetranychus  bimaculatus  Harvey. — The  first  is 
bright  cardinal  red,  while  the  two-spotted  mite  is  yellow,  pale  green 
or  reddish  and  often  has  two  or  six  dark  spots  on  the  dorsum.  Dust 
with  sulfur  or  spray  with  lime-sulfur  1-50  or  wettable  sulfur  (Form- 
ula 14),  or  commercial  sulfur  paste  10  pounds  to  100  gallons  of  water. 

Citrus  Thrips,  Scirtothrips  citri  (Moult.). — Small  pale  yellow  in- 
sects less  than  one-thirtieth  inch  long  working  in  blossoms  and  on 
leaves  and  fruit.  This  insect  is  most  satisfactorily  controlled  by  a 
2  per  cent  solution  of  commercial  lime-sulfur,  but  may  also  be  con- 
trolled by  using  the  Government  formula  for  pear  thrips  (Formula 
24)  or  by  applications  of  6  per  cent  nicodust.     A  combination  of  mis- 


22  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

cible  oil  and  lime-sulfur  is  recommended  by  some  for  killing  the  gray 
citrus  scale  (Coccus  citricola  Campb.)  and  the  citrus  thrips  at  the 
same  time. 

Fuller's  Rose  Beetle,  Pantomorus  fulleri  (Horn.).  —  A  small 
gray  snout  beetle  three-eighths  inch  long  which  attacks  young  buds 
and  foliage  of  citrus  trees.  The  adults  cannot  fly  and  may  be  kept 
off  the  trees  by  cotton  or  tanglefoot  bands  around  the  trunks. 

Mealybugs  (Various  Species  of  Pseudo coccus). — These  small,  flat, 
oval  insects,  covered  with  white  mealy  material,  are  well  known  to  most 
citrus  growers.  They  are  difficult  to  control,  but  may  be  most  satis- 
factorily handled  by  liberal  applications  of  carbolic  acid  emulsions 
(Formulas  26  and  26a)  and  by  miscible  oils.  Washing  with  water 
under  heavy  pressure  has  proved  satisfactory  under  certain  conditions. 
For  the  citrus  mealy  bug,  parasites  are  used  with  splendid  results 
along  the  coast.  The  control  of  ants  is  necessary  to  secure  beneficial 
results  from  natural  enemies.     See  "Ants. " 

Scale  Insects  (Many  Species). — Fumigation  with  hydrocyanic  acid 
gas  is  best,  although  some  orchardists  secure  good  results,  particularly 
for  soft  brown  and  gray  citrus  scales,  by  repeated  and  thorough  appli- 
cations of  various  strengths  of  distillate  emulsions  (Formulas  20  and 
23)  and  miscible  oils. 

CORN 

Boil  Smut  or  Common  Smut,  Vstilago  zeae  (Beckm.)  Ung. — Tender 
tissues  of  tassel,  ear,  or  stalk  swell  into  large  soft  masses,  which  dry 
out,  becoming  fragile  and  filled  with  black  dust.  Somtimes  gather- 
ing up  and  destroying  the  smutted  stalks  before  the  smut  balls  dry 
is  recommended.  Seed  treatment  is  not  effective.  Often  serious  in 
California.  Rotation  is  perhaps  useful.  Diseased  corn  trash  and 
manure  are  infectious. 

Ear  Mold,  Diplodia  zeae  (Schw.)  Lev.  and  Fusarium  sp. — The  ears 
mold  in  the  field,  the  kernels  becoming  crusted  together  and  light. 
Sometimes  bad  in  late  corn  in  shallow  soil.  Use  early  varieties.  Har- 
vest and  cure  as  early  as  possible.     Avoid  over-irrigation. 

Head  Smut,    Sphacelotheca  reiliana    (Kuchn.)    Clint. — Ear   and 

whole  top  of  plant  are  affected.     No  grain  formed.     See  ' '  Sorghum. ' ' 

Angoumoise  Grain  Moth. — See  "Grain." 

Armyworms  and  Cutworms.— See  "General  Subjects." 

Corn  Earworm,  Chloridea  obsoleta  (Fab.). — The  larvae  are  nearly 

two  inches  long  when  full  grown  and  vary  in  color  from  yellowish  to 

brownish,  with  longitudinal  gray  and  white  stripes  and  with  eight 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  23 

small  dark  tubercles  on  each  segment.  They  work  chiefly  on  the  corn 
in  the  ear,  but  may  also  attack  the  tassels  and  leaves.  Clean  up  and 
burn  refuse  in  the  field.  Plow  in  fall  or  early  spring  to  expose  and 
kill  the  pupae.  Repeated  dusting  of  ears  with  powdered  arsenate  of 
lead  one  part  to  four  parts  of  hydrated  lime  gives  some  relief. 

Granary  and  Rice  Weevils. — See  ' '  Grain. ' ' 

Grasshoppers. — See  "General  Subjects." 

Wireworms. — See  "General  Subjects." 

COTTON 

Bean  Thrips. — See  "Bean."  This  insect  usually  appears  on  the 
cotton  late  in  the  season,  when  the  injury  is  not  of  sufficient  importance 
to  justify  control.     Early  infestation  should  be  promptly  dealt  with. 

Corn  Earworm. — See  "Corn."  Attacks  the  cotton  bolls.  Sweet 
corn  is  sometimes  planted  as  a  catch  crop.  Dusting  with  powdered 
arsenate  of  lead  or  calcium  arsenate  gives  good  results. 

Cotton  Leaf  Perforator,  Buccidatrix  thurberiella  Busck. — The 
larvae  are  pale  or  dark  greenish  and  less  than  one-half  inch  long. 
When  disturbed  they  wriggle  violently.  The  work  consists  in  per- 
forating the  leaves  with  very  many  holes  so  as  to  almost  entirely 
consume  them.  The  larvae  pupate  in  small,  white-ribbed  cocoons 
attached  to  the  leaves  or  stems  of  the  plants.  The  adults  are  white 
with  black  dots  and  other  black  markings. 

This  insect  normally  feeds  upon  wild  cotton,  but  in  recent  years 
has  invaded  the  cotton  belt  of  the  Southwest,  and,  while  it  prefers  weak 
plants,  it  will  attack  perfectly  healthy  ones  as  well. 

Parasites  do  much  to  keep  the  insect  in  check  but  where  severe 
infestations  occur  dust  plants  with  calcium  arsenate  alone  or  with  lead 
arsenate,  one  part  to  four  parts  of  hydrated  lime.  From  20  to  30 
pounds  are  sufficient  for  an  acre  of  cotton. 

Red  Spider  or  Two-Spotted  Mite,  Tetranychus  telarias  Linn. — See 
"Bean." 

CUCUMBER 

Mildew,  Erysiphe  cichorearum  D.  C.  =  Oidium. — Fine  white  my- 
celium covers  the  leaves.  Dust  with  sulfur  at  first  appearance  or  with 
sulfur  nicodust  if  the  melon  aphis  is  also  present. 

Flea  Beetles  (Various  Species). — Small  flea-like  beetles  which 
jump  quickly  and  eat  small  holes  in  the  leaves.  Bordeaux  mixture 
(Formula  9)  as  a  repellent  is  the  best  control  measure.  This  treat- 
ment is  also  recommended  for  mildew. 


24  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Garden  Nematode. — See  ''General  Subjects." 

Melon  Aphis.— See  "Melon." 

Red  Spider  or  Two-Spotted  Mite.— See  "Bean." 

Western  Twelve-Spotted  and  Striped  Cucumber  Beetles,  Diabe- 
tica soror  Lee.  and  D.  trivittata  Mann. — The  former  is  a  small  green 
beetle  with  twelve  black  spots  on  the  back  and  is  often  mistaken  for  a 
ladybird;  the  latter  is  a  brown  beetle  with  three  black  lines  on  the 
dorsum.  The  white  larvae  feed  upon  the  roots  and  may  be  controlled 
by  pouring  on  the  roots  a  cup  of  40  per  cent  nicotine  sulfate  diluted 
1  to  1000  parts  of  water.  Bordeaux  mixture  (Formula  9)  is  of  con- 
siderable value  as  a  repellent.  Arsenate  of  lead  (Formula  2)  may  also 
be  used  with  good  effect. 

CURRANT,    GOOSEBERRY 

Mildew,  Sphaerotheca  mors-uvae  (Schw.)  B.  &  C. — A  fine  white 
mycelium  grows  over  the  young  leaves  and  shoots  and  checks  their 
development.  Serious  on  some  varieties.  The  best  treatment  is  to 
spray  with  lime-sulfur  1-33  when  buds  commence  to  open  and  two  or 
three  times  thereafter  at  intervals  of  10  to  14  days.  Where  serious 
cut  and  burn  diseased  tips  of  canes  while  dormant,  as  the  fungus  win- 
ters in  them  (from  U.  S.  D.  A.  Farmers'  Bull.  1024).  In  California, 
where  resistant  varieties  are  used,  a  dormant  spray  of  lime-sulfur  1-10, 
followed  by  dusting  with  sulfur  when  the  disease  first  appears,  has 
generally  been  effective. 

Currant  or  Gooseberry  Fruit  Fly,  Epochra  canadensis  Loew. — 
Small  white  maggots  in  the  fruit  at  picking  time.  Cultivate  thoroughly 
during  the  fall,  winter,  and  spring  months  to  expose  and  destroy  the 
hibernating  pupae. 

Flat-Headed  Apple  Tree  Borer.— See  "Apple." 

Imported  Currant  Borer,  Aegeria  tipuliformis  Clerck. — White 
caterpillars  nearly  one  inch  long  working  down  the  middle  of  the  stalks 
and  into  the  roots  of  the  plants.  Cut  out  and  burn  all  dead  and  in- 
fested canes  during  winter  and  remove  the  borers. 

Red  Spider  or  Two-Spotted  Mite,  Tetranychus  telarius  Linn. — See 
"Bean."  Dust  with  sulfur  or  spray  with  wettable  sulfur  (Formula 
14)  or  sulfur  paste  (Formula  13.) 

San  Jose  Scale. — See  "Apple." 

Combined  Spraying 
The  sulfur  sprays  will  control  both  the  mildew  and  the  red  spider. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  25 

DAHLIA 

Mildew,  Erysiphe  sp. — White  spots  spread  over  lower  leaves.     Not 
serious.     Dust  with  sulfur. 
Bean  Aphis. — See  "Bean." 
Western   Twelve-Spotted   Cucumber   Beetle. — See  "Cucumber." 

DATE 

Date  Palm  Scale,  Parlatoria  blanchardi  (Targ.). — A  small  gray 
and  white  scale,  less  than  one-sixteenth  inch  long,  often  occurring  in 
great  numbers  on  the  leaves.  It  may  be  controlled  by  cutting  away 
and  destroying  all  the  leaves,  burning  over  the  trunk  with  a  gasoline 
torch.  Offshoots  are  cleaned  up  by  heavy  fumigations  with  hydro- 
cyanic acid  gas.  This  insect  is  quarantined  by  the  Federal  Horticul- 
tural Board,  and  young  plants  may  be  obtained  only  from  uninfested 
territory. 

Dried  Fruit  Beetle.— See  "Prune." 

Indian  Meal  Moth. — See  "Prune."  This  insect  is  a  serious  pest 
to  dried  dates,  of  which  small  amounts  are  preferably  put  up  only  in 
insect-proof  containers  to  prevent  infestation. 

Marlatt  Scale,  Phoenico coccus  marlatti  Ckll. — A  red-bodied,  cot- 
tony covered  scale,  considerably  larger  than  the  date  palm  scale.  It 
is  chiefly  found  in  the  unfolding  leaves,  often  so  protected  as  to  be 
almost  impossible  of  control.  Fumigating  and  burning  over  the 
trunks  and  treating  liberally  with  carbolic  acid  and  oil  emulsions  give 
some  control,  but  eradication  on  a  tree  once  thoroughly  infested  is 
apparently  impossible.  This  pest  is  also  under  federal  quarantine, 
and  new  plants  may  be  obtained  only  from  uninfested  territory. 

Red  Spider.— See  "Citrus." 

FERNS 

Black  Scale  and  Plant  Lice. — Dip  the  plant  frequently  in  a  solu- 
tion of  40  per  cent  nicotine  sulfate,  1  part  to  600  parts  of  water. 

FIG 

Dropping  of  Fruit. — Usually  due  to  lack  of  caprification  by  the 
minute  fig  wasp  bringing  pollen  to  the  flowers  from  the  wild  or 
Capri  fig.  Applies  only  to  certain  varieties  as  the  Calimyrna.  Con- 
sult literature  on  fig  culture  and  authorities  on  the  subject. 


26  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Smut,  Aspergillus  niger  V.  Tiegh.  =  Sterigmatocystis  ficuum 
(Reich.)  Henn. — Caused  by  one  of  our  commonest  molds.  Infection 
occurs  in  ripening  fruit ;  if  at  an  early  stage,  the  fruit  rots,  if  later  it 
is  harvested.  In  extreme  cases  the  dried  fruit  is  merely  a  shell  filled 
with  purplish  black  dry  powder  which  may  be  puffed  out.  There 
are  all  gradations  to  the  condition  in  which  the  interior  of  the  fig 
is  merely  slightly  darkened.  Affected  fruit  is  said  not  to  give  an 
offensive  flavor,  nor  to  be  injurious  to  health.  Does  not  develop  in  the 
stored  dry  figs.     Remedies  not  yet  developed. 

Souring  and  Splitting. — Due  to  unfavorable  atmospheric  and  soil 
moisture  conditions.  Choose  suitable  localities  and  regulate  the  soil 
moisture  with  greatest  care. 

At  least  two  canker  diseases  are  known  in  California,  and  twig 
blight  is  caused  to  a  limited  extent  by  Sclerotinia  libertiana  and 
Botrytis  cincrea.  Frost  is  often  injurious  to  young  trees  which  make 
late  growth.  (See  "General  Subjects.")  None  of  these  appears  to 
be  serious. 

Branch  and  Twig  Borer. — See  ' '  Apricot. ' ' 

Mediterranean  Fig  Scale,  Lepidosaphes  ficus  (Sign.). — Scales  re- 
semble small  oysters  and  infest  the  limbs,  twigs,  leaves,  and  fruit. 
Spray  with  distillate  emulsion  (Formula  23),  miscible  oil  or  crude 
oil  emulsion  (Formula  18)  during  the  winter  when  the  trees  are 
dormant. 

Nematodes. — Becoming  increasingly  serious.  No  remedy  known. 
See  "General  Subjects." 

Pomace  or  Vinegar  Fly,  Drosophila  melanogaster  Meigen. — Small, 
slender,  whitish  maggots  and  brown  or  orange-colored  flies  one-tenth 
inch  long,  often  occurring  in  great  numbers  in  figs  on  the  trees  and 
on  the  drying  trays. 

GRAIN  (Barley,  Oats,  Wheat) 

Rust,  Puccinia  sps. — Pustules  of  pinhead  size,  round  or  elongated, 
break  through  the  surface  of  leaves  and  stems ;  mostly  reddish  at  first 
and  dusty ;  later  black.  Serious  in  heavy  grain  in  moist  situations  or 
seasons.     No  remedy  known  but  resistant  varieties  may  be  used. 

Smut,  Ustilago  sps.  and  Tilletia  sps. — Mature  grain  has  black  con- 
tent and  gives  off  characteristic  odor.  Seed  of  wheat,  barley,  oats, 
Sudan,  millet,  and  sorghum  should  be  carefully  cleaned  of  smut  balls, 
weed  seeds,  and  small,  cracked,  and  inferior  grains  before  treating. 
The  smut  balls  in  wheat  and  smut  masses  in  barley  may  be  cleaned  out 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  27 

in  fanning  mills  or  floated  out  in  water  and  skimmed  off.  Place  the 
cleaned  seed  in  half-filled  sacks  tied  at  the  end.  Immerse  these  sacks 
for  three  or  four  minutes  in  a  bluestone  solution  made  by  dissolving  1 
pound  of  bluestone  in  5  gallons  of  water  (Formula  11).  Drain  the 
sacks  until  dripping  no  longer  occurs,  then  dip  them  for  three  minutes 
in  a  milk  of  lime  made  by  slaking  1  pound  of  quicklime  in  10  gallons  of 
water.  The  lime  prevents  injury  to  the  germ  from  bluestone.  If 
quick-lime  cannot  be  secured,  air-slaked  lime,  1  pound  to  8  gallons  of 
water  may  be  used.  After  this  treatment  the  grain  should  be  spread 
out  to  dry,  after  which  it  may  be  planted  or  stored. 

Oats  are  especially  sensitive  to  bluestone,  and  for  them  it  is  better 
to  use  a  solution  of  formaldehyde,  1  pound  to  40  gallons  of  water,  for 
ten  minutes.  After  this  no  lime  dip  is  needed.  Barley  is  more  sensi- 
tive than  wheat  and  should  always  be  lime-dipped  after  treatment  with 
bluestone. 

Seed  scratched  or  injured  in  threshing  should  be  limed  after  dip- 
ping in  bluestone  solutions.  Scoured  seeds  should  not  be  dipped  in 
any  fungicidal  solution. 

Seed  wheat  and  barley  to  be  sown  in  dry  ground  or  to  be  stored 
longer  than  48  hours  must  not  be  treated  with  formaldehyde,  as  severe 
injury  may  follow. 

If  foggy  or  rainy  weather  is  liable  to  interfere  with  the  proper 
drying  of  lime-treated  seed,  heating  injury  may  be  avoided  by  soaking 
the  seed  for  10  or  15  minutes  in  water  before  dipping  in  the  bluestone 
solution.     The  lime  dip  may  then  be  omitted. 

Copper  carbonate  dust  has  been  highly  successful  in  controlling 
bunt,  but  is  not  so  successful  with  other  smuts.  The  copper  carbonate 
dust  does  not  cause  seed  injury,  and  appears  to  stimulate  growth. 
Dusted  seed  may  be  stored  dry  for  long  periods  without  injury  to 
seed.  A  number  of  serviceable  machines  for  applying  the  dust  are  on 
the  market.  Finely  powdered  bluestone  also  gives  good  smut  control, 
but  is  not  equal  to  copper  carbonate,  for  seed  injury  may  occur  in 
badly  scratched  or  broken  seed. 

Loose  smuts  of  wheat  and  sorghum  cannot  be  controlled  by  the 
above  treatment.  Loose  smuts  of  oats  and  barley  are  destroyed  by 
formaldehyde  solution  (1  pint  to  30  gallons  of  water),  soaking  for  10 
minutes.  Kernel  smut  of  sorghums  and  Sudan  grass  is  controlled  by 
soaking  the  seed  in  formaldehyde  solution,  as  above,  for  30  minutes  for 
grain  sorghums  and  60  to  90  minutes  for  sweet  sorghums  and  Sudan. 
Ergot  of  rye  and  rye  grass  is  controlled  by  floating  off  the  ergots  in  a 
strong  brine  solution  (40  pounds  salt  in  25  gallons  water)  and  rinsing 
with  clear  water,  or  by  holding  the  seed  for  a  year  before  sowing. 


28  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Angoumoise  Grain  Moth,  Sitotroga  cerealla  Oliv. — A  small  tawny 
moth  found  in  granaries.  The  pale  yellow  caterpillars  feed  within 
the  kernels  of  stored  grain  and  corn,  escaping  through  a  round  hole. 
Control  measures  are  the  same  as  for  the  granary  and  rice  weevils. 
See  below. 

Aphids  (Many  Species). — Aphids  often  seriously  attack  grain. 
Control  methods  are  usually  too  costly  to  be  practicable.  Cutting  is 
often  resorted  to  in  order  to  save  that  part  of  the  crop. 

Armyworms  and  Cutworms. — See  "General  Subjects." 

Grain  Mites,  Tyroglyphus  sps. — Pale-colored  mites,  smaller  than 
the  head  of  a  pin.  Frequently  found  in  grain  and  by-products. 
When  abundant,  they  appear  as  loose,  fluffy  masses  of  gray  powder 
as  the  cast  skins  are  mingled  with  the  living  mites.  Heat  is  the  most 
effective  remedy  and  should  be  used  if  practical.  (See  "Heat," 
p.  94.)  Fumigation  with  carbon  disulfid  may  also  be  used.  Screen- 
ing or  fanning  may  reduce  the  infestation  to  a  satisfactory  degree. 

Granary  Weevil,  Calandra  granaria  Linn.,  and  Rice  Weevil,  C. 
oryzae  Linn. — Small  brown  weevils  not  over  one-sixth  inch  in  length, 
attacking  the  grain  in  storage.  Fumigate  with  carbon  disulfid,  10 
to  30  pounds  to  1000  cubic  feet  of  air  space,  according  to  the  tightness 
of  the  container.  The  temperature  must  be  at  least  70°  F.  for  satis- 
factory results.  Hydrocyanic  acid  gas  may  also  be  used  as  a  f umigant, 
in  which  case  from  1  to  4  ounces  of  pure  sodium  cyanid  to  100  cubic 
feet  of  air  space  should  be  used.  Heating  the  grain  to  125°  F.  for 
several  hours  will  kill  all  the  weevils.  Keeping  the  grain  dry  and  well 
ventilated  will  largely  prevent  weevil  attack  in  storage. 

Grasshoppers. — See  ' '  General  Subjects. ' ' 

GRAPE,  RAISIN 

Coulure. — In  certain  varieties  notably  Muscat,  the  flowers  some- 
times fail  to  set  fruit.  Interplanting  with  other  varieties  to  im- 
prove pollination  is  recommended.  Also  vigorous  sulfuring  during 
blossoming  to  prevent  mildew  favors  the  setting  of  fruit. 

Crown  Gall  =  Black  Knot,  Bacterium  tumefaciens  S.  and  T. — 
Rough  galls  form  on  canes  and  trunks  above  ground;  often  serious. 
Girdled  stems  become  weakened  and  die.  Bad  in  cold  situations  and 
following  frosty  seasons.  If  spoiled  parts  are  removed  in  time, 
new  shoots  will  grow  up  from  below.  Control  not  worked  out,  but 
something  can  be  done  by  surgery.  Bordeaux  spray  in  winter  should 
be  tried  as  preventive.     See  "General  Subjects,"  p.  55. 


Circular  265]  PLANT  DISEASE  AND  PEST   CONTROL  29 

Little  Leaf ,  Apoplexy,  Black  Measles,  Obscure  Diseases. — See 
''Physiological  Diseases,"  p.  57,  under  "General  Subjects." 

Mildew,  Uncinula  spiralis  B.  &  C.  =  l\  necator  <Schw.)  Burr. — 
White  mycelium  spreads  over  young  leaves,  canes  and  fruits,  checking 
growth ;  the  leaves  are  deformed  and  may  drop ;  the  surface  of  the 
fruit  hardens  and  darkens  and  the  fruit  often  cracks,  or  may  drop. 
Dust  vrith  sulfur  when  the  shoots  are  about  6  inches  long  and  again 
just  before  the -blossoms  open,  being  careful  not  to  miss  a  single  leaf. 
If  the  vines  were  affected  the  previous  year  do  not  wait  until  the 
mildew  appears.  In  cool  or  moist  locations  a  third  sulfuring  when 
the  grapes  are  as  large  as  peas  and  a  fourth  when  they  are  two-thirds 
grown  may  be  necessary.  In  these  later  treatments  the  sulfur  should 
be  dusted  only  on  the  fruit  and  the  centers  of  the  vines.  If  the  larvae 
of  leaf -hoppers  are  present  use  nico-sulfur  instead  of  sulfur. 

Achemon  Sphinx  Moth,  Pholus  achemon  (Drury). — Large  green 
and  pinkish  caterpillars  with  oblique  whitish  bars  on  the  sides.  Often 
abundant  and  doing  great  damage  by  stripping  the  vines. '  Adult 
moths  dull  gray  with  brown  marks  and  pink  hind  wings.  Spray  vines 
with  arsenate  of  lead  (Formula  2),  to  which  is  added  1  pint  of  40 
per  cent  nicotine  sulfate  to  every  200  gallons,  or  dust  with  powdered 
arsenate  of  lead.  1  part  to  4  parts  of  hydrated  lime  or  flowers  of  sulfur. 

Armyworms  and  Cutworms. — See  "General  Subjects." 

California  Grape  Root  Worm,  Bromius  ooscurus  (Linn.) — The 
adult  beetles  are  black  or  brown  and  three-sixteenths  inch  long.  They 
eat  long  slender  holes  in  the  leaves.  The  small  white  grubs  feed  on 
the  roots  of  the  vines.  Cultivate  thoroughly  close  to  the  vines  during 
the  winter  to  kill  hibernating  larvae.  As  soon  as  the  beetles  appear  in 
the  spring  spray  with  arsenate  of  lead,  6  pounds  of  paste  or  3  pounds 
of  powder  to  100  gallons  of  water,  or  dust  with  1  part  of  powdered 
arsenate  of  lead  to  4  parts  of  hydrated  lime  or  sulfur. 

Dried  Fruit  Beetle. — On  raisins,  see  "Prune." 

Grape  Leaf-hopper,  Erythroneura  comes  (Say). — The  immature 
forms  or  nymphs  are  white  or  pale  yellow,  while  the  adults  are  pale 
yellow  with  numerous  small  reddish  marks  all  over  the  dorsum.  All 
forms  feed  on- the  under  side  of  the  leaves,  causing  them  to  turn  yellow 
and  drop  prematurely.  Clear  weeds  and  refuse  from  around  the 
vineyards  and  practice  clean  culture  to  reduce  the  number  of  over- 
wintering adults.  Before  the  young  nymphs  develop  wings  spray 
thoroughly  with  nicotine  and  soap  (Formula  27).  or  with  the  follow- 
ing:: 40  per  cent  nicotine  sulfate,  1  pound;  liquid  soap,  13  gallon  (hard 


30  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

soap,  2  pounds) ;  water,  200  gallons.  The  young  and  adults  may  also 
be  killed  by  thoroughly  dusting  with  a  10  per  cent  nicodust,  or  a 
6  per  cent  nicosulfur  dust,  which  latter  will  also  control  mildew. 

Grape  Phylloxera,  Peritymbia  vitifoliae  (Fitch). — The  presence 
of  the  phylloxera  is  indicated  by  weak  and  dying  vines.  It  usually 
occurs  in  spots.  The  insect  is  a  minute,  yellow  louse  which  feeds  on 
the  roots.  To  disinfect  cuttings  or  rootings  before  planting,  dip  in 
hot  water  122°  F.  for  five  minutes.  For  permanently  resistant  vines, 
graft  European  varieties  on  certain  American  roots.  (See  Circular 
No.  226,  Calif.  Agr.  Exp.  Sta.,  Univ.  of  Calif.,  Dec,  1920.) 

Grasshoppers. — See  "General  Subjects." 

Indian  Meal  Moth. — On  raisins,  see  "Prune." 

Mealybug,  Pseudococcus  maritimus  Ehr.  =  P.  bakeri  Essig. — 
Easily  distinguished  by  the  small  oval,  flat  bodies  covered  with  white 
cotton-like  wax  and  by  the  cottony  egg  masses  among  the  bunches  of 
grapes.  ,  Difficult  of  control,  but  best  results  have  been  obtained  by 
burning  sulfur  under  a  tent  over  the  vines.  (See  Monthly  Bull.,  Cal. 
State  Dept.  Agr.,  Sacramento,  Vol.  IX,  p.  26,  1920).  Also  see  "Pear." 

HOLLYHOCK 

Rust,  Puccinia  malvacearum  Mont. — Prominent  red  sori  or  pus- 
tules push  out  on  the  lower  surface  of  the  leaves  and  on  petioles  and 
stems,  often  causing  distortion.  Fertilize  and  water  freely  to  promote 
vigorous  growth. 

Destroy  all  old  plants  and  start  anew  from  seed  at  least  every 
two  years.     Some  strains  appear  to  be  resistant. 

The  Painted  Lady  Butterfly,  Vanessa  caryae  Hubn. — The  yellowish 
or  black  spiny  caterpillars,  which  are  about  one  inch  long,  feed  on 
the  leaves,  which  they  draw  together  with  webs  for  protection.  Con- 
trol is  best  accomplished  by  using  40  per  cent  nicotine  sulfate,  1  part 
to  600  parts  of  water,  and  spraying  the  plants  thoroughly. 

HOP 

Hop  Aphis,  Phorodon  humuli  (Schr.). — A  pale  green  aphid  at- 
tacking the  young  shoots  and  leaves.  Dust  thoroughly  and  as  often 
as  necessary  with  5  per  cent  nicodust  or  spray  until  injury  ceases  with 
nicotine  and  soap  (Formula  27.) 

Hop  Flea  Beetle,  Psylliodes  punctulata  Mels. — A  small  green  or 
bronze   metallic  beetle,   one-tenth   inch  long,   attacking  the   foliage. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  31 

Jumps  quickly  when  disturbed.  The  most  efficient  method  of  control 
consists  in  putting  tanglefoot  bands  around  the  bases  of  the  vines  and 
around  the  poles.  These  not  only  prevent  the  beetles  from  climbing 
the  vines  but  catch  great  numbers  of  them. 

Red  Spider  or  Two-Spotted  Mite.— See  "Bean." 


LAWNS 

Earth  Worms. — Earth  worms  or  angle  worms  frequently  cover 
golf  greens  with  casts  of  earth,  which  are  undesirable  in  such  a 
place.  To  cause  the  worms  to  come  to  the  surface,  apply  corrosive 
sublimate,  mixed  as  follows,  and  then  sweep  up  the  worms  and  remove 
them : — 

1  lb.  corrosive  sublimate. 

1  gallon  boiling  water. 

Let  cool  for  one  hour;  then  add  4  gallons  of  cold  water.  Use 
2%  pints  of  this  solution  to  a  barrel  of  water,  and  apply  to  greens 
with  a  sprinkler.  See  p.  90  for  precautions  in  the  use  of  corrosive 
sublimate.    This  is  a  dangerous  poison. 

Weeds. — Fertilize  well.  Use  a  solution  of  nitrate  of  soda,  strong 
enough  to  kill  the  tops  but  not  the  roots — about  3  to  5  pounds  to 
100  gallons  af  water,  depending  on  the  kind  of  grasses  in  the  lawn. 

Wireworms. — Lime  water  applied  to  the  brown  places  in  the  lawn 
will  drive  out  wireworms. 

LOQUAT 

Pear  Blight,  Bacillus  amylovorus  (Burr.)  Detoni. — Limb  and  body 
blight  is  sometimes  very  severe.     See  "Pear." 

Scab,  Fusicladium  eryohotryae  Sciala. — Resembles  scab  of  pear 
and  apple,  but  is  more  injurious  to  expanding  foliage.  (See  ' ' Pear. ") 
Control  is  not  developed  but  sprays  for  pear  in  foliage  may  probably 
be  used. 

Green  Apple  Aphis. — See  "Apple." 

San  Jose  Scale. — See  "Apple." 

MELON  (Casaba,  Cantaloupe,  Pumpkin,  Squash,  Watermelon). 

Blossom  End  Rot. — Is  presumably  associated  with  soil  or  climatic 
conditions.  Sometimes  severe.  There  is  indication  of  resistance  in 
some  varieties. 


32  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Wilt,  Fusarium  sp. — Well-grown  watermelon  plants  wilt  and  die, 
leaving  the  field  nearly  bare.  Plant  on  fresh  soil.  Watermelons  can- 
not be  grown  for  several  years  on  infected  ground.  Other  melons  are 
not  often,  if  ever,  affected  in  California. 

Flea  Beetles. — See  ' '  Cucumber. ' ' 

Melon  Aphis,  Aphis  gossypii  Glover. — A  small,  dark  green  louse 
occurring  in  great  numbers  on  the  plants  and  doing  great  damage. 
Destroy  first  infested  plants  as  soon  as  discovered  in  spring  or  spray 
with  nicotine  sulfate,  40  per  cent,  1  part  to  1000  parts  of  water.  A 
5  per  cent  nicodust  also  gives  very  good  results  and  is  much  more 
easily  and  quickly  applied. 

Nematode. — See  * '  General  Subjects. ' ' 

Squash  Bug,  Anasa  tristis  De  Geer. — The  young  bugs  are  gray 
with  black  antennae,  legs,  and  thorax;  the  adults  of  a  uniform  dull 
grayish-brown  above,  mottled  yellowish  beneath,  and  about  three- 
quarters  inch  long.  Control  measures  should  be  directed  against  the 
immature  forms,  and  consist  in  the  use  of  1  part  of  40  per  cent 
nicotine  sulfate  to  600  parts  of  water.  A  10  per  cent  nicodust  kills 
many.  Hand  picking  the  adults  in  the  spring  is  successful  in  small 
gardens. 

Western  Twelve-Spotted  and  Striped  Cucumber  Beetles. — See 
"Cucumber." 

NURSERY  STOCK 

Failure  to  Grow  After  Planting  in  Orchard. — Very  rarely  due  to 
specific  disease.  Usually  caused  by  freezing,  drying,  or  water  soaking 
of  trees  before  or  after  planting ;  planting  too  deep ;  cold,  wet,  or  hot 
weather  after  planting ;  or  some  other  condition  unfavorable  to  growth. 
Bare  roots  are  very  sensitive  to  slight  freezing  and  injured  trees 
at  best  start  tardily  and  grow  in  a  sickly  way.  Buy  from  the 
nearest  reputable  nursery.  Pay  for  good  trees  and  see  that  they 
are  handled  and  planted  carefully.  Replant  all  that  do  not  grow 
well  the  first  season. 

Citrus  Trees. — For  scale  insects,  defoliate  and  fumigate  with 
hydrocyanic  acid  gas.  (See  p.  89.)  Rejecting  infested  stock  is  the 
only  safe  procedure. 

Deciduous  Trees. — For  borers  and  other  insects,  fumigate  with 
hydrocyanic  acid  gas.  Rejecting  infested  stock  is  the  only  safe 
procedure. 

Nematode,  Crown  Gall. — Very  carefully  avoid  planting  affected 
trees.  If  a  large  percentage  of  a  plot  of  trees  is  affected,  those  appar- 
ently healthy  are  of  doubtful  value.     See  ''General  Subjects.7 7 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  33 

Pythiacystis  Canker  or  Brown  Rot  of  Lemon,  Pythiacistis  citroph- 
thora  S.  &  S. — Dead  spots  up  to  several  inches  long  develop  on  the 
trunk  or  branches,  mostly  above  the  bud  union.  Caused  by  soil 
infection  under  very  wet  conditions.  Spray  trees  with  Bordeaux 
mixture  before  digging  and  after  healing  in.  Soil  for  healing  in 
should  be  well  drained  or  under  cover.  Active  only  in  very  wet 
seasons. 

OAT.     See  Grain 

OLIVE 

Armillaria,  Wood  Decay. — See  under  ''General  Subjects,"  p.  53. 

Die-back  =  Exanthema. — Bushy  phase  characterized  by  repeated 
death  of  terminal  buds  and  branching  out  below ;  leaves  show  deform- 
ities. In  die-back  phase  there  is  usually  dropsy-like  puffing  of  bark 
on  branches  and  limbs  and  unusual  prominence  of  lenticels  in  the 
smooth  bark,  with  dying  back.  Secure  uniform  moisture  and  good 
drainage.  Add  organic  material  to  soil  by  green  manure  crops,  mulch, 
or  manure.  Replace  olives  with  plums,  peaches,  or  other  crop  where 
die-back  is  very  bad.  See  "Physiological  Diseases,"  under  "General 
Subjects. ' ' 

Dry  Rot,  Bitter  Pit. — Dry  spots  appear  in  the  flesh  of  the  fruit. 
(See  "Physiological  Diseases,"  under  "General  Subjects.")  No 
effective  treatment  known  except  good  general  care. 

Olive  Knot  =.  Tuberculosis,  Bacterium  savastanoi  E.  F.  Smith  = 
Pseudomonas  oleae. — Rounded,  rough  swellings,  from  very  small  up 
to  several  inches  in  diameter,  appear  on  twigs,  limbs,  trunk,  or  roots, 
mostly  at  leaf  scars  or  wounds,  also  rarely  on  fruit  pedicels  and  leaves. 
Cut  out  thoroughly  at  first  appearance  and  disinfect.  (See  "Pear 
Blight"  and  "Crown  Gall.")  The  Mission  is  more  resistant  than  the 
Manzanillo  or  some  oil  varieties. 

Peacock  Spot,  Cycloconium  oleaginum  Cast.  —  Blackish  round 
spots,  one-eighth  to  one-quarter  inch  in  diameter,  on  the  surface  of 
green  leaves  but  not  killing  the  darkened  area.  Is  apparently  of 
very  slight  importance  in  California. 

Black  Scale,  Saissetia  oleae  (Bern.). — See  "Apricot."  Attacking 
chiefly  the  twigs.  Spray  with  distillate  emulsion  (Formula  23)  or 
miscible  oil,  December  to  February. 

Branch  and  Twig  Borer,  Poly  coon  confertus  Lee. — See  ' '  Apricot. ' ' 
This  is  often  a  serious  pest  of  young  olive  trees. 


34  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Ivy  or  Oleander  Scale,  Aspidiohcs  hederae  Vail. — A  small  circular, 
flat,  gray  scale  occurring  on  the  leaves  and  fruit,  somtimes  causing 
discolored  spots  on  the  ripening  olives.     Control  as  for  black  scale. 

Olive  Bark  Beetle,  Leperisinus  californicus  Swaine. — The  small 
white  larvae  work  in  the  cambium  layer  just  under  the  bark  and  the 
adults  bore  small,  round  exit  and  entrance  holes  through  the  bark. 
Occurs  in  the  southern  part  of  the  state.  Burn  prunings  and  remove 
all  dead  and  infested  portions  of  the  trees. 

ONION 

Downy  Mildew,  Peronospora  schleideni  Ung. — Areas  on  leaves  or 
stems  show  a  violet-tinted  fuzz.  These  areas  rapidly  fade  and  collapse 
if  the  weather  is  moist,  and  the  disease  may  spread  rapidly.  Not  suc- 
cessfully controlled  in  wet  seasons.  Bordeaux  mixture  found  useful 
in  some  cases;  it  should  be  used  with  resin  fish-oil  soap  or  other 
spreader.     See  ' '  Spreaders, ' '  pp.  68-69  ;  also  ' '  Asparagus. ' ' 

Pink  Root,  Fusariam  malli  Taub. — Young  plants  are  stunted  and 
older  plants  are  injured,  bulb  formation  is  interfered  with  and  the 
crop  reduced.  Roots  diseased  turn  pink.  Avoid  infected  soil,  or 
if  not  entirely  possible  keep  plants  growing  as  well  as  possible  at 
all  times.  Where  plants  are  grown  in  a  seedbed  and  transplanted, 
use  healthy  soil,  or  disinfect  with  formaldehyde  or  steam,  p.  95. 

Scullions. — Plants  fail  to  form  bulbs,  the  stalks  remaining  thick 
and  green.  May  be  due  to  poor  seed  or  to  a  check  in  growth.  Plant 
at  a  suitable  season  so  that  development  may  be  continuous.  Cutting 
off  seed  stalks  and  breaking  over  tops  when  crop  is  maturing  may 
help. 

Armyworms  and  Cutworms. — See  "General  Subjects." 

Onion  Maggot,  Hylemyia  antiqua  Meig. — Small,  white  maggots 
attacking  the  onions  beneath  the  ground.  Practice  clean  culture  and 
destroy  all  refuse  onions  in  the  fall.  Plow  and  cultivate  thoroughly 
during  winter  and  spring.  Considerable  protection  is  gained  by 
spraying  the  plants  repeatedly  with  carbolic  acid  emulsion.  (Form- 
ula 26,  diluting  stock  solution  1  to  40.) 

Onion  Thrips,  Thrips  tabaci  Lind. — Minute,  slender,  pale  yellow 
insects  occurring  in  great  numbers  on  the  leaves,  causing  them  to  turn 
gray  and  wither.  Spray  with  1  part  of  40  per  cent  nicotine  sulfate 
to  800  parts  of  water  or  apply  5  per  cent  nicodust. 

Wireworms. — See  "General  Subjects." 


* 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  35 


PEA 

Bacterial  Blight  or  Bacteriosis,  Pseudomonas  pisi  Sack. — Exten- 
sive, watery,  olive  green  blisters  appear  on  stems  and  leaf  bases  in 
wet  weather,  following  cold.  Some  affected  areas  dry  up,  others  kill 
the  stem.  Where  the  injury  does  not  go  too  far  down,  new  stems 
grow  from  below.  In  some  wet  situations  practically  every  plant 
has  been  killed.  Control  not  developed,  but  the  trouble  is  worse  in 
cold  wet  situations. 

Blight  or  Spot,  Mycosphaerella  pinodes  Berk.  &  B\ox.=Ascochyta. 
— Sunken  dead  spots  form  on  pods,  leaves,  and  stems,  one-quarter 
inch  or  less  in  diameter;  center  of  spot  on  pod  becomes  gray  or 
pinkish,  with  a  dark  border;  on  leaf  and  stem  spots  are  more  often 
merely  dark.  Young  stems  may  be  killed.  Experiments  indicate 
spraying  is  impractical.  Keep  pea  crop  and  diseased  material  off 
the  land  for  two  years.  Seed  infection  rare  in  California.  Avoid 
too  low,  wet  land. 

Downy  Mildew,  Peronospora  trifoliorum  De  Bary. — Resembles 
downy  mildew  of  Alfalfa.  (See  p.  1.)  Common  at  the  close  of  the 
rainy  season,  but  apparently  not  serious. 

Mildew  or  Powdery  Mildew,  Erysiphe  polygoni  D.  C. — Powdery 
white  growth  spreads  over  the  foliage,  injuring  plants.  Troublesome 
in  summer  or  when  rains  are  light  or  lacking.  Dust  with  sulfur  on 
first  appearance  or  nicosulfur  dust  if  aphids  are  abundant,  and 
repeat  if  necessary. 

Armyworms  and  Cutworms.    See  "General  Subjects." 

Pea  Aphis,  Macrosiphum  pisi  (Kalt.). — A  large  green  aphid  at- 
tacking the  terminal  shoots  and  leaves  of  the  vines.  It  is  difficult  of 
control  because  of  the  expense  involved,  but  may  be  killed  by  repeated 
applications  of  a  10  per  cent  nicodust  or  a  nicotine  spray  (Formula 
27a)  or  a  6  per  cent  nicosulfur  dust  to  also  control  mildew. 

Pea  Weevil,  Bruchus  pisorum  Linn. — A  small  gray  and  white 
weevil  attacking  the  pea,  much  as  the  bean  weevil  attacks  the  bean, 
but  the  pea  weevil  infests  the  peas  in  the  field  and  the  adults  do  not 
emerge  until  the  following  spring.  Unlike  the  bean  weevil,  however, 
it  never  reinfests  stored  peas.  Treatment  is  the  same  as  for  bean 
weevil.     See  "Bean." 


36  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


PEACH 

Armillaria,  Wood  Decay,  Crown  Gall,  Nematode. — See  "General 
Subjects,"  p.  53. 

Brown  Rot,  Sclerotinia  cinerea  (Bon.). — See  "Apricot."  Some- 
times causing  decay  of  late-ripening  fruit  in  moist  regions  near 
the  coast.  Control  for  the  fruit-rot  stage  recommended  in  Eastern 
states  consists  of  spraying  of  self -boiled  lime-sulfur  (Formula  15A). 
The  last  application  should  be  made  a  month  or  more  before  picking 
so  that  the  stain  will  not  remain  on  the  ripe  fruit. 

Leaf  Curl,  Exoascus  deformans  Fcl. — Young  leaves  are  attacked 
and  become  much  thickened  and  ruffled.  Tips  of  shoots  are  some- 
times similarly  affected  and  rarely  areas  on  fruit.  Affected  tissue 
is  light  or  highly  colored;  it  becomes  powdery  white  and  dies  early 
in  the  summer.  Trees  may  be  much  injured  by  loss  of  foliage. 
Sprays  for  blight  should  control  this,  or,  if  blight  is  not  present, 
only  the  spring  application  need  be  made.  Some  failures  in  control 
may  be  due  to  too  late  application  of  spray. 

Little  Leaf. — See  "Physiological  Diseases,"  p.  57,  under  "Gen- 
eral Subjects." 

Peach  Blight,  Coryneum  oeijerinchii  Oud. — See  also  "Apricot," 
' '  Almond, "  "  Cherry. ' '  Buds  are  killed  during  winter,  sunken  round 
spots  are  killed  in  one-year  twigs,  and  in  spring  a  shot-hole  effect 
appears  on  young  leaves;  later  the  twig  spots  gum  profusely  and 
gradually  heal  over  unless  the  twig  is  killed.  Very  serious  in  interior 
valley  and  foothill  districts  in  moist  winters.  Spray  with  Bordeaux 
(Formula  9),  or  lime-sulfur  1-10  between  November  15  and  Decem- 
ber 15.  Repeat  with  lime-sulfur  or  Bordeaux  when  buds  swell 
and  before  first  blossoms  begin  to  open.  Peaches  cannot  be  sprayed 
with  these  materials  after  the  leaves  appear  without  danger  of  serious 
injury. 

Powdery  Mildew,  Sphaerotheca  pannosa  var.  persicae  (Wallr.) 
Lev. — Young  foliage  becomes  covered  with  white  powder  and  growth 
may  be  checked.  Large  powdery  white  areas  may  appear  on  the  fruit 
and  later  turn  dark  and  check.  Spray  with  lime-sulfur,  as  for  leaf 
curl.  Prune  to  thin  foliage.  Dust  with  sulfur  at  first  indication  of 
mildew  and  repeat  as  necessary. 

Rust,  Transchelia  punctata  (Pers.)  Arth.  =  Puccinia  pruni,  Pers. 
— Sometimes  causes  trouble  in  the  canneries  through  interfering  with 
peeling  of  fruit,  small  hard  spots  remaining  in  the  surface.  See 
"Almond,"  "Apricot,"  "Plum." 


Circular  265]  PLANT  DISEASE  AND  PEST   CONTROL  37 

Black  Peach  Aphis,  Aphis  persicae-niger  Smith. — A  shiny  black 
aphid  occurring  in  great  numbers  on  the  young  tender  shoots.  Spray 
with  nicotine  and  soap  (Formula  27)  or  dust  with  5  per  cent  nicodust 
as  soon  as  the  insects  appear. 

Black  Scale.— See  "Apricot." 

Branch  and  Twig  Borer,  Polycaon  confertus  Lee. — See  ' '  Apricot. ' ' 

Brown  Apricot  Scale. — See  "Apricot." 

California  Peach  Borer,  Aegeria  opalescens  Hy.  Edw. — White  cat- 
terpillars  attaining  a  length  of  one  and  one-half  inches  which  burrow 
under  the  bark  at  the  base  of  the  trees,  often  extending  their  tunnels 
down  into  the  bases  of  the  main  roots.  Often  serious,  as  they  may 
completely  girdle  the  trees.  Dig  out  the  worms  carefully  in  the  fall 
and  spring  and  paint  over  the  wounds  with  a  good  asphaltum  paint. 
Use  para-dichlorobenzene  in  summer  and  fall.  See  methods  of  treat- 
ment p.  80. 

Cankerworms. — See  "General  Subjects." 

Flat-Headed  Apple  Tree  Borer.— See  "Apple." 

Peach  Rust  Mite,  Phyllocoptes  cornutus  Banks. — A  microscopic 
mite  causing  a  silvering  of  the  leaves.  Spray  in  winter  when  the  trees 
are  dormant  or  when  buds  swell  in  the  spring  with  lime-sulfur  1-10 
to  kill  mites  hibernating  in  buds. 

Peach  Twig  Borer,  Anarsia  lineatella  Zeller. — A  small,  dark- 
reddish  caterpillar,  scarcely  one-half  inch  long,  which  burrows  into 
and  kills  the  young  tender  tips  of  the  twigs  and,  later  on,  may  infest 
the  fruit  to  some  degree.  The  minute  young  forms  hibernate  in  small 
cells  in  the  bark  and  are  effectively  killed  in  the  early  spring  of  the 
year  with  lime-sulfur  1-10  applied  just  as  the  blossom  buds  begin  to 
open,  which  is  before  the  larvae  are  able  to  enter  the  expanding  leaf 
buds. 

The  investigations  carried  out  by  W.  P.  Duruz  have  led  to  the 
following  more  complete  recommendations  for  the  control  of  the 
peach  twig-borer  on  peaches  and  apricots: 

1.  Spray  with  commercial  liquid  lime-sulfur  at  the  rate  of  1 
gallon  to  9  of  water,  plus  basic  arsenate  of  lead  powder,  3  pounds  to 
100  gallons,  in  the  spring  at  the  pink  stage,  that  is,  just  previous 
to  blossoming.  This  combination  will  control  diseases  and  insect 
pests  other  than  the  peach  twig-borer.  Because  of  the  frequent 
damage  resulting  from  lime-sulfur  in  coastal  districts,  it  is  con- 
sidered best  not  to  use  this  spray  on  apricots.  Therefore  Bordeaux 
mixture,  7-8-50,  plus  basic  arsenate  of  lead,  3  pounds  to  100  gallons. 


38  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

seems  to  be  the  best  combination  for  apricots  when  brown  rot  or 
shot-hole  fungus  and  peach  twig-borer  are  to  be  controlled.  This 
later  spray  also  should  be  applied  at  the  pink  stage. 

2.  Nicotine  sulfate,  %  of  a  pint  to  100  gallons  of  water,  with  3 
pounds  of  soap  as  a  spreader,  is  a  good  remedy  for  the  peach  twig- 
borer,  and  may  be  used  alone  in  a  few  limited  cases  where  diseases 
and  other  insects  are  not  troublesome.  This  is  specially  recommended 
for  apricot  trees  which  may  -be  injured  by  lime-sulfur  or  arsenical 
sprays. 

3.  A  summer  spray  of  arsenate  of  lead,  basic  or  neutral  (never 
acid),  at  the  rate  of  3  pounds  to  100  gallons  of  water  with  % 
pounds  of  casein  spreader,  may  be  used  as  an  additional  insurance 
against  "wormy"  fruit.  This  spray  should  be  applied  not  less 
than  two  weeks  before  the  fruit  is  picked. 

4.  Too  much  emphasis  cannot  be  placed  upon  the  necessity 
of  proper  spraying  at  the  right  time.  It  is  essential  to  cover  the  entire 
surface  of  the  tree,  particularly  the  newer  and  outer  portions  of 
the  branches.  Use  at  least  175  pounds  pressure  and  preferably  250 
pounds. 

5.  All  prunings  should  be  collected  and  particularly  the  small 
and  newer  wood  should  be  burned  before  spring,  because  this  material 
harbors  the  larvae. 

6.  Cull  fruit  should  not  be  carelessly  left  about  the  orchard 
or  packing  house.  All  wormy  fruit  should  be  collected  and  properly 
disposed  of.  It  should  be  fed  promptly  to  pigs  or  other  stock,  or 
destroyed  by  burning  or  burying.  A  quick  and  simple  manner  of 
destroying  worms  in  the  cull  fruit  is  to  place  the  discarded  fruit 
in  a  pile  or  in  a  trench,  saturate  with  oil  or  cover  with  wood,  and 
ignite.  The  heat  resulting  from  the  fire  will  be  sufficient  to  kill 
the  larvae  in  the  fruit.  Another  means  of  destroying  the  larvae  is 
to  place  the  cull  fruit  in  a  caldron  of  boiling  water  for  15  minutes. 

Red  Spider.— See  "Almond"  and  "Prune." 

San  Jose  Scale. — See  "Apple." 

Shot  Hole  Borer.— See  "Apricot." 

Tent  Caterpillars. — See  "General  Subjects." 

Wheat  Thrips,  Frankliniella  tritici  (Fitch). — This  minute  orange 
and  yellow  thrips  often  does  considerable  damage  to  the  young  fruit 
at  blossoming  time  and  later.  For  control  see  pear  thrips  under 
"Pear." 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  39 

Combined  Spraying 

Two  applications  of  lime-sulfur  as  recommended  above  for  peach 
blight  will  control  all  of  the  usual  diseases  and  pests  of  the  peach 
in  California  which  can  be  reached  by  any  spray  treatment,  but 
lime-sulfur  has  occasionally  been  reported  as  causing  injury  when 
applied  in  the  bloom  and  may  not  be  effective  for  control  of  leaf 
curl  when  applied  late. 

PEAR 

Black  End. — Is  presumably  a  physiological  disease  comparable  to 
blossom  end  rot  of  tomatoes.  No  recommendation  as  yet  except  to 
give  good  care,  especially  as  to  drainage. 

Black  Leaf. — Resembles  blight  in  effect;  bark,  however,  is  not 
reddish  and  juicy  when  cut  into,  but  with  dry  black  spots  or  areas. 
(See  "Sour  Sap,"  under  "General  Subjects.")  Shallow  soil  and 
summer  drought  appear  to  have  particular  significance  in  connection 
with  this  trouble.  A  peculiar  condition  sometimes  develops  on  indi- 
vidual trees  in  which  dark  points  develop  in  one-year  bark.  These 
persist  and  become  hard,  raised  and  enlarged  until  the  whole  surface 
may  be  much  roughened  and  hardened.  In  certain  dry  soils  in  the 
south  a  peculiar  drying  back  of  twigs  occurs.  The  drying  progresses 
to  a  certain  point  and  new  shoots  start  out  below.  Making  the 
moisture  supply  of  the  soil  more  constant  is  believed  to  have  greatly 
helped  this  condition.    See  "Sour  Sap,"  p.  57. 

Blight,  Bacillus  amylovorus  (Burr.)  Detoni. — Tender  growth  be- 
comes watery,  darkens  rapidly,  wilts,  and  dies ;  usually  minute  beads 
of  viscid  material  exude ;  they  dry  in  the  same  form  and  show  a  solid 
mass  of  bacteria  under  the  microscope  when  moistened  in  water;  in 
heavier  bark  the  exudate  may  be  more  copious,  or  it  may  be  lacking; 
the  diseased  tissue  may  be  recognized  by  cutting  into  it.  Watery, 
reddish,  or  somewhat  dark  streaked  areas  indicate  blight.  Any 
succulent  part  of  the  top,  body  or  root  may  be  attacked.  Cut  out 
all  affected  parts  very  thoroughly.  Work  especially  on  "hold-over" 
in  large  limbs,  trunks,  and  roots  during  the  winter.  Disinfect  tools 
and  cuts  freely.  A  new  system  is  being  largely  used  in  which  only 
the  outer  bark  is  cut  away,  leaving  the  cambium.  Keep  close  watch 
to  check  new  development  of  infection.  Mercuric  cyanid  and  corro- 
sive sublimate  combined,  1  part  of  each  to  500  of  water*  (Formula 

*  Mr.  Leonard  Day  of  our  Pomology  Division  recommends  instead  of  water 
in  the  above  formula  1  part  water  in  3  parts  glycerine.  The  disinfectants  are 
dissolved  in  the  1  part  of  water  and  the  3  parts  of  glycerine  added.  Hot  water 
dissolves  the  chemicals  more  readily  than  cold.  This  spreads  and  penetrates 
better  than  the  water  solution. 


40  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

28a,  p.  90),  is  widely  used  for  disinfection.  Keep  all  suckers  and 
spurs  off  of  root  and  body.  In  new  plantings  in  blight  regions,  top- 
work  on  resistant  varieties.  Surprise,  Ussuriensis,  and  others  are 
being  used  and  promise  well. 

Avoid  stimulating  excessive  and  succulent  growth.  Clean  up  or 
destroy  infected  apple,  quince,  loquat,  Christmas  berry  and  related 
plants  in  the  neighborhood. 

Scab,  Venturia  pyrina  Aderh.  =  Fusicladium. — Dark,  velvety 
mold  patches  appear  on  young  fruit  and  leaves;  badly  affected  fruit 
drops,  but  much  remains,  the  dark  areas  becoming  hard  and  rough  and 
often  cracked,  deforming  the  fruit.  Plow  under  all  old  leaves  as 
thoroughly  as  possible.  Spray  with  lime-sulfur  1  to  12,  or  Bor- 
deaux (Formula  9)  just  as  the  winter  buds  first  loosen  to  show  the 
individual  flower  buds.  Repeat  just  before  the  first  flowers  open. 
Where  there  is  danger  of  late  scab  infection,  follow  directions  under 
1 '  Combined  Spraying. ' ' 

Many  varieties  of  pears  are  self-sterile  or  partly  or  occasionally 
so.  Cross  pollination  is  sometimes  essential  and  perhaps  always  bene- 
ficial for  the  Bartlett.  Frost  may  cause  flowers  to  drop  or  fruit  to 
develop  russet  areas  or  bands.  Premature  starting  of  blosson  buds 
from  unfavorable  conditions  may  simulate  thrips  injury,  causing 
them  to  be  loose  and  dry  in  winter  and  to  come  out  imperfectly  in 
spring.  Glut  morceau  fruit  becomes  injured  and  deformed  or  drops, 
apparently  from  cold,  when  others  are  not  injured. 

Baker's  Mealybug,  Pseudococcus  maritimus  Ehrh.  =  P.  bakeri 
Essig. — Small,  oval,  flat  insect  less  than  one-quarter  inch  long  and 
covered  with  white  powdery  wax  and  normally  with  several  white,  tail- 
like filaments  nearly  half  as  long  as  the  body.  The  egg  sacs  look  like 
small  masses  of  cotton.  The  insects  occur  under  the  bark,  on  the  under 
side  of  limbs,  in  cracks,  wounds,  and  in  the  blossom  end  of  the  fruit. 
Control  measures  are  difficult  and  consist  of  repeated  applications  of 
crude  carbolic  acid  and  distillate  emulsion  (Formula  26a)  during  the 
winter  months  and  until  the  buds  begin  to  open  in  the  spring.  Scrape 
the  rough  bark  from  the  trunks  and  larger  limbs  so  as  to  expose  the 
mealybugs  to  fhe  spray.  If  the  fruit  is  infested,  spray  during  the 
summer  with  water  under  heavy  pressure  to  wash  the  bugs  away. 

Branch  and  Twig  Borer. — See  "Apricot." 

Brown  Apricot  and  Other  Soft  Scales.— See  "Apricot." 

Cankerworms. — See  "General  Subjects." 

Cherry  or  Pear  Slug. — See  "Cherry." 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  41 

Codling  Moth. — See  "Apple."  The  control  of  this  insect  on  pears 
is  not  so  difficult  as  on  apples,  but  thorough  work  is  necessary  to  insure 
clean  fruit,  particularly  in  districts  where  large  acreages  of  pears  are 
grown. 

Fruit  Tree  Roller.— See  "Apple." 

Green  Apple  Aphis. — See  "Apple." 

Italian  Pear  Scale,  Epidiaspis  piricola  Del  G. — A  small,  gray,  cir- 
cular scale,  the  body  being  dark  red,  usually  occurring  under  the 
moss  or  old  bark;  but  it  may  cover  the  trunks  and  all  of  the  main 
branches  of  the  tree.  Causes  sunken  areas  in  old  limbs  and  greatly 
weakens  the  tree.  Spray  in  the  winter  months,  preferably  in  January 
and  February,  with  crude  oil  emulsion  (Formula  18),  distillate  sprays 
(Formulas  20  to  23),  or  miscible  oils.  The  crude  oil  emulsions  are 
preferable.  Thoroughly  drench  the  limbs  and  trunks.  (See  Cir.  No. 
224,  Calif.  Agr.  Exp.  Sta.,  Univ.  Calif.,  Dec,  1920.) 

Pear  Leaf  Blister  Mite,  Eriophyes  pyri  (Pagen.). — A  microscopic 
mite  causing  pinkish  and  yellowish  blisters  or  marks  on  the  young 
terminal  leaves  and  occasionally  reddish  blotches  on  the  young  fruit. 
Spray  in  November  or  February  with  lime-sulfur  1-10  to  kill  hiber- 
nating mites  in  buds. 

Pear  Root  Aphis,  Eriosoma  languinosa  (Hartig). — A  small  dark 
aphid  covered  wtih  white  cottony  material  and  greatly  resembling 
the  woolly  apple  aphis,  but  attacks  only  the  pear  roots.  For  control 
see  woolly  aphis  under  "Apple."  Eliminate  young  stunted  trees  and 
replant  healthy  ones.  The  Japanese  root  is  much  more  resistant  to 
this  pest  than  the  French.  Use  para-dichlorobenzene  in  fall.   See  p.  80. 

Pear  Thrips,  Taeniotlirips  inconsequens  Uzel. — Small,  slender, 
black  insect  one-sixteenth  inch  long,  appearing  before  or  at  the  time 
the  blossom  buds  begin  to  open  and  continuing  until  after  blooming 
season.  The  young  or  white  thrips  work  in  the  late  blossoms,  but 
chiefly  on  the  young  fruit  and  leaves.  Spray  as  often  as  necessary 
with  the  government  formula  (Formula  24)  or  dust  repeatedly  with 
5  per  cent  or  6  per  cent  nicodust.  Watch  for  adult  black  thrips  as 
soon  as  the  buds  begin  to  open  and  apply  control  measures  as  soon 
as  any  number  of  the  insects  appear.  (See  Cir.  No.  223,  Calif.  Agr. 
Exp.  Sta.,  Univ.  Calif.,  Nov.,  1920.) 

Red  Humped  Caterpillar. — See  ' '  Prune. ' ' 

San  Jose  Scale. — See  "Apple."  Treatment  for  the  Italian  pear 
scale  above  will  also  suffice  for  this  insect. 


42  university  of  california — experiment  station 

Combined  Spraying 

1.  For  scale  of  any  kind  and  for  moss  and  a  general  clean-up,  use 
a  winter  spray  of  lime-sulfur  1-10,  crude  oil  emulsion  (Formula  18), 
or  miscible  oil. 

2.  For  scab  and  thrips  use  Bordeaux  mixture  (Formula  9),  or 
lime-sulfur  1-12  as  cluster  buds  are  opening,  adding  an  extra  10 
pounds  of  lime  and  1  pound  of  40  per  cent  nicotine  sulfate  to  each  200 
gallons  of  spray.  Oil  sprays  should  not  be  mixed  with  lime-sulfur  or 
Bordeaux  mixture  for  this  purpose. 

3.  For  scab  and  thrips,  repeat  "2"  when  first  blossoms  are  about 
to  open. 

4.  For  codling  moth  and  late  scab  infection,  spray  when  petals  are 
falling  with  8  pounds  of  lead  arsenate  in  200  gallons  of  1-30  lime- 
sulfur  or  200  gallons  of  Bordeaux  mixture. 

PLUM,  PRUNE 

Armillaria,  Wood  Decay,  Crown  Gall,  Sour  Sap  and  Physiological 
Diseases. — See  "General  Subjects,''  p.  53. 

Brown  Rot. — Not  often  serious.     See  "Apricot." 

Leaf  Spot,  Coryneum  beijerinckii  Oud. — See  "Apricot,"  "Peach." 
and   "Almond." 

Plum  Pockets,  Exoascus  pruni  Fcl. — This  disease  is  as  yet  very 
local.  Young  fruits  puff  up  early,  becoming  large  and  bladdery, 
then  wither  and  fall.  Remove  all  diseased  fruits  and  twigs  and  burn. 
Spray  as  for  leaf  curl  of  peach. 

Rust,  Transchelia  punctata  (Pers.)  Arth.=^Puccinia  pruni  Pers. — 
Small,  dark  brown,  powdery  dots  appear  on  the  lower  sides  of  leaves 
with  corresponding  yellow  dots  above.     Not  observed  to  be  serious. 

Unfruitfulness. — See  also  under  "Pear"  and  "Almond."  The 
University's  Division  of  Pomology  is  adding  constantly  to  our 
knowledge  of  the  relations  of  varieties  for  efficiency  in  cross  fertiliza- 
tion. Growers  should  keep  carefully  posted  on  these  results.  Vari- 
eties may  be  wrongly  chosen,  bees  may  be  lacking,  premature  starting 
and  failure  of  buds  may  occur. 

Black  Scale. — See  "Apricot." 

Brown  Apricot  Scale. — See  ' '  Apricot. ' ' 

Branch  and  Twig  Borer. — See  ' '  Apricot. ' ' 

California  Peach  Borer. — See  ' '  Peach. ' ' 

Cankerworms. — See  "General  Subjects." 


CIRCULAR  265]  PLANT  DISEASE  AND  PEST  CONTROL  43 

Cherry  Fruit  Sawfly. — See  "Cherry."  Also  attacks  varieties  of 
plums. 

Citrus  Red  Spider,  Tetranychus  citri  McGregor. — See  "Common 
Red  Spider,"  p.  44. 

Dried  Fruit  Beetle,  Carpophilus  hemipterus  (Linn.). — A  small 
black  beetle  less  than  one-quarter  inch  long  with  a  reddish  spot 
near  the  middle  of  the  dorsum.  The  adults  and  small  yellowish 
or  whitish  larvae  feed  on  the  dried  fruit  and  continue  to  breed  indefin- 
itely in  storage.  They  may  be  controlled  by  fumigation  as  recom- 
mended for  grain  weevil.     See  "  Grain. " 

Flat-Headed  Apple  Tree  Borer.— See  "Apple." 

Fruit  Tree  Leaf  Roller.— See  "Apple." 

Indian  Meal  Moth,  Plodia  inter punctella  Hiibn. — The  caterpillars 
are  white  or  pinkish  and  about  one  inch  long.  They  feed  on  the  dried 
fruit,  through  which  they  work  their  way  to  all  parts,  leaving  behind 
a  trail  of  excrement,  webbing,  and  spoiled  fruit.  Their  presence  is 
usually  first  indicated  by  webbing  on  the  fruit  or  around  the  sides  of 
the  container.  The  adults  are  small,  slender,  silvery  gray  moths  with 
the  apical  ends  of  the  wings  coppery.  This  insect  is  controlled  in  the 
same  way  as  the  granary  weevil.  (See  " ' Grain. ")  Dipping  the  fruit 
in  scalding  water  prior  to  packing  kills  all  forms  of  this  insect.  Small 
packages  of  dried  fruit  should  be  made  insect  proof  to  prevent  infes- 
tation in  warehouses  and  storerooms. 

Italian  Pear  Scale.— See  "Pear." 

Mealy  Plum  Louse,  Hyalopterus  arundinis  (Fabr.). — A  pale  green 
aphid  covered  with  a  fine  white  mealy  wax ;  it  collects  in  great  numbers 
on  the  under  side  of  the  leaves  of  tender  shoots  in  May  and  June. 
Spray  with  6  pounds  of  fish  oil  soap  to  200  gallons  of  water,  or  use 
nicotine  soap  spray.  (Formula  27.)  The  soap  alone  appears  to  give 
as  satisfactory  results  as  the  nicotine  soap  spray  and  is  much  cheaper. 

Peach  Twig  Borer. — See  "Peach." 

Pear  Thrips.— See  "Pear." 

Red-Humped  Caterpillar,  Schizura  concinna  S.  &  H. — The  cater- 
pillars are  beautifully  lined,  reddish,  black  and  yellow  with  a  con- 
spicuous red  hump  on  the  back.  They  feed  in  large  colonies  and 
may  entirely  defoliate  individual  limbs  or  entire  trees  during  the 
spring  and  again  in  the  fall  of  the  year.  They  spin  no  webs  and 
are  not  to  be  confused  with  the  tent  caterpillars  which  appear  in 
the  spring  and  the  webworms,  in  the  fall.  Control  measures  consist 
in  cutting  out  and  burning  the  entire  colonies  when  small  or  in 
spraying  with  arsenate  of  lead  as  for  codling  moth  or  better  in  dust- 
ing the  infested  trees  with  1  pound  of  powdered  arsenate  of  lead 


44  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

thoroughly  mixed  with  4  pounds  of  hydrated  lime.  The  dusting  may 
be  effectively  done  with  either  a  hand  or  power  machine. 

Red  Spider  or  Almond  Mite. — See  "Almond." 

San  Jose  Scale. — See  "Apple." 

Tent  Caterpillars. — See  "General  Subjects." 

Common  Red  Spider,  Tetranychus  telarius  Linn. — This  small,  pale 
green  or  yellow  mite,  with  from  two  to  six  dark  spots  on  its  back, 
appears  in  mid  and  late  summer  and  does  great  damage  to  plum  and 
prune  trees  by  causing  the  leaves  to  fall  prematurely.  Dusting  and 
spraying  as  recommended  for  the  almond  mite  (see  "Almond")  should 
be  done  very  thoroughly  and  continued  until  the  first  good  rains  occur 
in  the  fall. 

Tussock  Moth.— See  "Apple." 

Combined  Spraying 

For  scale,  moss,  and  a  general  clean-up,  spray  in  winter  with  crude 
oil  emulsion.     (Formula  26.) 

POTATO 

Black  Heart. — Dark  clouded  areas  appear  in  the  flesh  and  may 
dry  out,  leaving  cavities.  Due  to  high  temperature  or  lack  of  oxygen 
or  the  two  combined.  Occurs  mostly  in  storage,  but  may  develop 
before  digging. 

Brown  Streak. — Tubers  show  a  brown  ring  or  streaks  in  the  flesh 
when  cut  into.  Apparently  due  to  climatic  conditions — high  temp- 
erature and  drought.  Affected  seed  may  produce  a  healthy  crop. 
See  "Physiological  Diseases,"  p.  57. 

Jelly  End,  Soft  Rot,  Leak. — Very  soft  or  watery  rots;  are  due 
to  infection  in  wounds  with  several  fungi,  Pythium,  Rhizopus,  etc. 
Avoid  injury  and  bruising  in  digging. 

Potato  Late  Blight,  Late  Rot,  Phytophthora  infestans  (Mont.) 
De  Bary. — Translucent  spots  appear  on  the  leaves  and  stems,  which 
spread  rapidly  till  entire  top  is  wilted  and  prostrate.  The  tubers  show 
sunken  spots  at  digging  and  rot  in  storage.  Spray  with  Bordeaux 
mixture    (Formula  9)    immediately  after  rains. 

Rhizoctonia  or  Black  Scurf,  Corticium  vagum  B.  and  C.  =  Rhiz- 
octonia. — Dark,  reddish-brown  scabs  are  found  on  the  tubers.  These 
may  be  scraped  off,  leaving  the  surface  smooth.  Underground  parts 
are  killed  in  some  cases,  destroying  plants,  reducing  the  number  of 
tubers,  or  causing  various  symptoms  in  the  tops,  sometimes  with 
aerial  tubers.  The  fungus  is  of  widespread  occurence  in  soil  and 
attacks  many  plants.    See  ' '  Beans, "  "  Damping  Off, ' '  p.  55,  etc. 


CIRCULAR  265]  PLANT  DISEASE  AND  PEST  CONTROL  45 

For  tuber  diseases  in  general  secure  seed  from  healthy  fields 
and  reject  any  tubers  showing  appreciable  amounts  of  scab,  rhizoc- 
tonia, wilt  (as  shown  by  dark  fibres  in  section  of  the  stem  end)  or 
other  suspicious  symptoms.  If  scab  and  rhizoctonia  are  feared,  dip 
in  a  solution  of  corrosive  sublimate  (Formula  28,  p.  90)  for  1% 
hours  before  cutting.  This  solution  should  be  placed  in  wooden  or 
earthenware  (not  metal)  containers  and  should  be  used  only  4  or  5 
times;  also  the  potatoes  should  be  clean  as  possible  before  dipping. 
Do  not  use  potatoes  treated  with  corrosive  sublimate  for  food.  If 
only  scab  is  feared,  the  tubers  may  be  dipped  in  a  solution  of  formal- 
dehyde, 1  pound  to  30  gallons  of  water  for  2  hours.  The  solution 
may  be  used  repeatedly,  and  is  not  spoiled  by  contact  with  metal. 

Potato  pathology  in  recent  years  has  become  highly  intricate  and 
control  measures  must  be  adapted  to  local  conditions.  Healthy 
seed,  rotation  of  crops,  preparation  of  soil  and  management  are 
of  great  importance.  See  your  farm  advisor  and  authorities  on 
potato  culture. 

Scab,  Actinomyces  scabies  (Thaxter)  Giiss.  =  Oospora. — The  com- 
mon rough,  corky  spots  in  the  surface  of  tubers  which  are  made 
unsightly.  Underground  parts  of  the  growing  plant  are  also  injured 
to  some  extent.  Said  to  be  favored  by  alkaline  soil,  or  the  addition 
of  lime  or  manure  in  excess,  and  retarded  by  the  plowing  down  of 
a  green  cover  crop.  Use  clean  seed  and  dip  in  a  fungicide.  See 
' '  Rhizoctonia. ' ' 

Wilt  and  Dry  Rot,  Fusarium  sp. — Plants  are  affected  as  in  severe 
drought,  the  leaves  ripening  prematurely.  Tubers  appear  sound,  but 
often  show  a  ring  of  darkened  fibres  when  the  stem  end  is  cut  across. 
Low  temperature  in  general  retards  rot  associated  with  wilt.  So 
far  as  possible,  use  seed  from  healthy  fields. 

Aphids  (Various  Species). — Dust  thoroughly  with  5  per  cent  nico- 
dust  or  spray  with  1  part  of  40  per  cent  nicotine  sulfate  to  800  parts 
of  water. 

Armyworms  and  Cutworms. — See  "General  Subjects." 

Flea  Beetles  and  Leaf  Beetles. — See  "Melon."  Use  Bordeaux 
mixture  (Formula  9)  as  a  repellent,  or  a  nicodust  lead  arsenate 
mixture. 

Garden  Nematode  or  Eelworm. — This  microscopic  round  worm 
produces  a  pimply  or  warty  surface  on  the  potato  and  small  brown 
dots  just  beneath  the  skin.  Plant  only  clean  seed  and  avoid  infested 
soil. 

Grasshoppers. — See  "General  Subjects." 

..... 


46  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Potato  Stalk  Borer,  Trichobaris  trinotata  Say. — The  larvae  are 
small,  pale  yellow  or  white,  and  not  over  one-half  inch  long ;  they  bore 
throughout  the  middle  of  the  stalks,  causing  them  to  wilt  and  die. 
The  adults  hibernate  in  the  old  dry  stalks,  which  should  be  raked  up 
after  digging  and  burned.  This  affords  an  almost  perfect  control  if 
thoroughly  done. 

Potato  Tuber  Moth,  Phthorimaea  operculelld  (Zeller). — The  full- 
grown  caterpillars  are  white  or  pinkish  and  not  over  three-quarters 
inch  long.  They  make  numerous  burrows  just  under  the  skin  and 
throughout  the  tubers,  continuing  to  work  as  long  as  the  tubers  are 
available.  Infestation  may  occur  in  the  field  or  in  storage.  Hill  up 
well  around  the  growing  plants  and  remove  the  potatoes  as  soon  as 
dug  to  prevent  infestation  in  the  field.  Store  in  a  clean,  uninfested 
place.  If  infested,  fumigate  with  20  to  30  pounds  of  carbon  bisulfid 
to  every  1000  cubic  feet  of  air  space  at  a  temperature  70°  F.  or  over. 
Plant  only  clean  seed. 

Tomato  and  Tobacco  Worms. — See  "Tomato." 

Wireworms. — See  "General  Subjects." 

Combined  Spraying 

Bordeaux  mixture  will  control  not  only  the  flea  beetles  but  will 
materially   aid   in  subduing  many  fungus   diseases. 

PUMPKIN.     See  "Melon" 

ROSE 

Cold  Injury. — Many  plants  are  found  in  spring  with  dark-stained 
leaves  or  small  distorted  and  sickly  foliage,  due  to  chilling  of  tender 
tissue  of  shoots,  which  start  growth  too  early  in  winter.  Delay 
pruning  until  February  or  later.  Prune  rather  heavily  and  stimulate 
vigorous  growth  by  general  culture  measures. 

Mildew,  Sphaerotheca  pannosa  (Wallr.)  Lev.  and  S.  humuli 
(D.  C.)  Burr.  =  Oidium. — White,  powdery  mildew  spreads  over 
young  stems  or  leaves,  causing  distortion  or  dropping  of  leaves  and 
discoloration;  severe  in  cool  coast  districts.  Spray  with  lime-sulfur 
1-10  before  the  spring  growth  starts.  Use  dry  sulfur,  sulfur  paste, 
or  lime-sulfur  1-35  when  disease  first  appears. 

Aphids  (Various  Species). — Two  common  aphids  usually  infest 
roses:  the  large  green  and  pink  Macrosiphum  rosae  (Linn.),  which 
commonly  attacks  the  tender  tips  and  buds,  and  the  small  green 
Myzaphis  rosarum  (Walk.),  which  works  on  all  parts  of  the  plant  and 
produces  large  quantities  of  honey  dew,  resulting  in  the  smutting  of 


CIRCULAR  265]  PLANT  DISEASE  AND  PEST  CONTROL  47 

the  plants.  Both  may  be  effectually  controlled  by  dusting  liberally 
with  5  per  cent  nicodust,  by  spraying  with  nicotine  sulfate,  40  per 
cent,  1  part  to  1000  parts  of  water,  or  by  thoroughly  hosing  off  the 
plants  every  two  or  three  days  with  a  strong  water  pressure  and  a 
coarse  nozzle. 

Fuller's  Rose  Beetle.— See  "Citrus  Fruits." 

Raspberry  Horntail. — See  ' '  Bush  Fruits. ' ' 

Rose  Scale. — See  ' '  Bush  Fruits. ' '  Spray  infested  portions  of  the 
plants  during  the  winter  months  with  miscible  oils. 

Rose  Snout  Beetle,  Bhynchites  bicolor  Fabr. — A  small  red  and 
black  snout  beetle,  scarcely  one-quarter  inch  long,  which  punctures 
the  buds  of  roses,  causing  numerous  holes  in  the  petals  when  the 
flowers  open.  Jar  beetles  in  pan  of  oil  in  the  early  mornings.  A 
10  per  cent  nicodust  has  given  good  control  in  some  places. 

Combined  Spraying 

For  fungus  diseases  and  aphids,  a  40  per  cent  nicotine  sulfate  may 
be  added  to  sulfur  sprays  as  given  above,  and  a  sulfur  nicodust  may 
also  be  used  for  mildew  and  aphis. 

SNAPDRAGON 

Rust,  Puccinia  antirrhini  D.  &  H. — Brown  rust  sori  break  out 
through  the  leaf  and  stem.  Infection  is  usually  heavy  and  the  plant 
becomes  unsightly  and  dies.  Water  and  fertilize  freely  to  stimulate 
growth.  When  the  disease  becomes  severe  destroy  badly  affected 
plants  and  clean  up  thoroughly  in  the  fall.  Start  with  clean  seed- 
lings. Pentstemon  is  a  fairly  good  substitute  for  snapdragon,  and 
does  not  rust. 

Aphids. — Dust  thoroughly  with  5  per  cent  nicodust. 

SORGHUM,  SUDAN  GRASS,  AND  BROOM  CORN 

Head  Smut,  Sphacelotheca  reiliana  (Kuhn.)  Clint. — Whole  head 
or  panicle  becomes  a  black  mass.  Method  of  treatment  not  yet 
developed.  Affected  plants  should  be  destroyed  at  first  appearance. 
Affects  also  corn. 

Kernel  Smut,  Sphacelotheca  sorghi  (Lk.)  CI. — Kernels  form  en- 
larged grains  which  become  fragile  and  filled  with  a  black  powder. 
Controlled  by  seed  treatment.     See  ' '  Grain. ' ' 

Aphids  (Various  Species). — See  "Grain." 

Armyworms  and  Cutworms. — See  "General  Subjects." 

Granary  and  Rice  Weevils. — See  "Grain. 

Grasshoppers. — See  "General  Subjects. 


t  •> 


48  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

SPINACH 

Armyworms  and  Cutworms. — See  "General  Subjects.' '  Poison 
bran  mash  sown  broadcast  over  the  fields  has  proved  very  success- 
ful in  completely  protecting  young  plants. 

Beet  or  Spinach  Leaf  Miner,  Chortophila  hyoscyami  Panzer. — 
Small  white  maggots  mining  the  leaves  and  causing  discolored  areas. 
Keep  down  all  weeds  about  the  fields,  burn  refuse  tops,  harvest  as 
early  as  possible.  Winter-grown  spinach  usually  escapes  the  attacks 
of  this  insect. 

Flea  Beetles. — See  ' '  Cucumber. ' ' 

Grasshoppers. — See  ''General  Subjects." 

Melon  Aphis.— See  " Melon." 

SQUASH.     See  Melon. 

STRAWBERRY 

Leaf  Spot,  My cosphaerella  frag ariae  (Tul.)  Linn.  =  Ramularia. — 
Dead  spots  on  leaves,  one-quarter  inch  or  less  in  diameter  with  red 
borders;  if  abundant  it  lowers  the  vitality  of  the  plants.  Clean  up 
and  burn  the  leaves  in  late  fall.  Spray  with  Bordeaux  mixture 
(Formula  9)  if  the  disease  becomes  serious. 

Leaf  and  Stem  Rot. — Symptoms  are  those  of  acute  drought  injury ; 
plants  die  back  in  hot  weather  and  inferior  growth  comes  up  later  with 
poor  production;  roots  are  killed  off,  apparently  by  poor  soil  condi- 
tions. Use  less  water.  Improve  drainage.  Wash  out  alkali  in  winter 
by  flooding. 

Gray  Mold,  Botrytis  rot.— See  "Bush  Fruits." 

Strawberry  Aphis,  Myzus  fragaefolii  Ckll. — A  very  small  pale 
yellow  aphis  occurring  in  great  numbers  on  the  under  sides  of  the 
leaves,  and  often  smutting  the  foliage.  Defoliate  the  plants  in  winter. 
Dust  liberally  with  5  per  cent  nicodust  as  soon  as  the  aphids  appear, 
applying  it  to  the  under  side  of  the  leaves  with  an  upturned  discharge 
pipe. 

Strawberry  Crown  Moth,  Aegeria  rutilans  H.  Edw. — A  white  cat- 
erpillar one-half  inch  long  or  less  boring  into  the  crown  of  the  plant, 
causing  it  to  turn  yellow  and  die.  Remove  and  burn  infested  plants 
as  soon  as  discovered.     Be  sure  of  clean  nursery  stock. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  49 

Strawberry  Flea  Beetle,  Haltica  ignita  Illiger. — A  bright  metallic, 
golden,  green,  or  purplish  flea  beetle,  one-sixth  inch  long,  feeding  upon 
the  leaves  of  the  plants.  Use  Bordeaux  mixture  (Formula  9)  as  a 
repellent. 

Strawberry  Leaf  Beetle,  Paria  canella  (Fabr.). — A  small  brown 
beetle  with  black  markings  on  the  dorsum  and  averaging  one-eighth 
inch  long.  The  adults  eat  numerous  small  irregular  holes  in  the 
leaves,  while  the  small  white  larvae  attack  the  roots.  It  is  a  severe 
pest,  and  should  be  eradicated,  if  possible,  by  destroying  all  infested 
vines  and  thoroughly  sterilizing  the  soil  by  steam  or  carbon  bisulfid. 
Established  infestations  may  be  reduced  by  thoroughly  spraying  with 
arsenate  of  lead  (Formula  2),  or  by  dusting  with  1  part  of  basic 
powdered  arsenate  of  lead  to  4  parts  of  powdered  hydrated  lime. 

Strawberry  Root  Weevil. — The  one  known  infestation  of  Otio- 
rhynchus  rugifrons  Gyll.  in  California  is  quarantined.  Secure  plants 
from  uninfestated  district.  Report  any  suspicious  cases  to  the  State 
Department  of  Agriculture,  Sacramento,  Calif. 

Two-Spotted  Mite,  Tetranychus  telarius  Linn. — See  "Bean"  and 
1 '  Prune. ' '  Though  ordinarily  controlled  with  dry  sulfur,  this  method 
cannot  be  used  on  strawberries  because  of  the  severe  burning  to  the 
foliage.  Very  small  amounts  of  sulfur  in  the  ditches  between  the  rows 
have  afforded  some  relief. 

SWEET  POTATO 

Black  Rot,  Sphaeronema  fimbriatum  (E.  &  H.)  SdLQe.=Ceratocystis. 
— Black  spots  appear  on  sprouts  and  circular  black  spots  on  surface 
of  potatoes,  with  tissue  below  greenish.  Affected  potatoes  are  bitter 
when  cooked.     Spreads  in  storage.     See  "Wilt." 

Foot  Rot,  Plenodomus  destruens  Harter. — Brown  to  black  spots 
appear  on  stems  near  surface  of  soil  late  in  season  and  plants  finally 
wilt,  usually  not  producing  potatoes.  Also  a  brown  firm  rot  of  pota- 
toes often  starting  in  wounds.     See  "Wilt." 

Scurf,  Monilochaetes  infuscans  E.  &  H. — A  brown  discoloration  or 
spotting  occurs  on  the  surface  of  the  potatoes  rendering  them  less 
attractive  and  more  liable  to  dry  out  in  storage.     See  ' '  Wilt. ' ' 

Soft  Rot,  Rhizopus  nigricans  Ehr. — Mainly  a  storage  trouble;  rot 
starts  at  injuries  and  progresses  rapidly;  decayed  part  becomes  cov- 
ered with  white  mold  which  later  turns  black.  Avoid  bruising.  Dry 
well  before  storing.  For  long  keeping,  pack  in  dry  sand.  Moisture 
and  temperature  requirements  of  sweet  potatoes  in  storage  are  differ- 
ent from  those  of  most  other  products  and  must  be  carefully  observed. 


50  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 

Wilt  or  Stem  Rot,  Fusarium  sp. — Leaves  become  paler  than  nor- 
mal; plants  wilt  and  die;  stems  have  the  fibres  blackened  and  this 
shows  also  in  the  stem  end  of  the  potato  as  a  blackening  when  cut 
across. 

Stem  and  root  diseases  of  sweet  potatoes  require  siviilar  treatment. 
Hotbeds  which  have  been  used  previously  for  sweet  potatoes  should 
be  cleaned  out  and  soaked  with  formalin  1  pound  to  30  gallons  of 
water.  The  soil  used  should  be  from  some  place  where  sweet  potatoes 
have  never  been  present  or  should  be  disinfected.  (See  p.  95.)  The 
manure  should  have  no  remains  of  sweet  potatoes  in  it.  Plants  and 
potatoes  are  both  infectious.  Where  wilt  is  present,  select  seed  pota- 
toes in  the  field  before  frost,  cutting  across  the  stems  and  rejecting 
all  hills  which  show  black  rings.  Store  all  seed  potatoes  separate  from 
the  main  crop,  where  contamination  may  not  spread  to  them.  Where 
diseases  are  serious,  dip  the  seed  in  corrosive  sublimate  as  for  white 
potatoes  (see  p.  45),  except  that  the  time  of  soaking  must  not  exceed 
5  to  10  minutes.  Where  diseases  become  troublesome,  rotate  crops, 
planting  no  sweet  potatoes  for  three  to  six  years. 

TOBACCO.     See  "Tomato" 

TOMATO.     See  also  ' '  Potato ' ' 

Blossom  End  Rot. — Dry  spot  appears  at  blossom  end  of  green  fruit 
and  develops  slowly.     Avoid  drought  or  irregular  irrigation. 

Damping-off. — See  "General  Subjects." 

Fruit  Decays. — In  California  due  mostly  to  common  molds  which 
gain  access  in  some  mechanical  injury  and  develop  on  the  way  to 
market.  Remove  all  refuse  fruit  to  a  safe  distance  from  the  packing 
house.     Avoid  mechanical  injuries  in  the  fruit. 

Late  Blight,  Late  Rot,  Phytophthora  infestans  (Mont.)  De  B. — In 
late  moist  weather  large  vague  spots  appear  on  the  leaves,  at  first  dark 
and  watery,  becoming  slightly  frosted  with  emerging  fungus  threads 
below,  then  deteriorating  rapidly.  Similar  spots  appear  on  the  fruit, 
not  well-marked  at  first,  but  the  fruit  spoils  rapidly.  Spray  with 
Bordeaux  mixture  (Formula  9)  immediately  after  rains. 

Western  Blight. — Plants  become  pale;  leaves  roll  upward,  expos- 
ing purplish  veins;  plants  become  worthless  and  most  of  them  die. 
No  control  has  been  developed  as  yet. 

Wilt,  Fusarium  sp. — Plants  in  the  field  turn  yellow  and  die  often 
after  reaching  considerable  size.  A  dry  rot  is  found  in  the  stem 
and  roots.  Secure  clean  soil  for  seedbed  or  disinfect  soil  and  beds. 
(See  p.  95.)     Rotate  crops.    Resistant  varieties  are  being  sought. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  51 

Armyworms  and  Cutworms. — See  " General  Subjects." 

Grasshoppers. — See  "General  Subjects.' ' 

Darkling  Ground  Beetles,  Blapstinus  sp.  and  Eurymetopon  bicolor 
Horn. — Small,  dull  black  or  bluish-black  beetles,  scarcely  more  than 
one-quarter  inch  long,  living  in  the  soil  and  responsible  for  much  dam- 
age to  young  plants  shortly  after  transplanting.  Before  resetting, 
wrap  the  stems  of  the  young  plants  from  roots  to  tops  with  tissue  paper 
so  as  to  have  three  or  four  thicknesses  for  protection,  or  scatter  poison 
bran  mash  (Formula  4)  over  the  ground  at  planting  time. 

Flea  Beetles. — Dust  with  powdered  arsenate  of  lead,  1  part  to  4 
parts  of  dry  lime  or  sulfur,  nicodust  and  arsenate  of  lead,  or  spray 
with  Bordeaux  mixture.     (Formula  9.) 

Garden  Nematode. — See  "General  Subjects." 

Tomato  Worm,  Protoparce  sexta,  Joh.  and  Tobacco  Worm,  P. 
quinquemaculata  Haw. — Large  green  worms  often  attaining  a  length 
of  four  inches.  They  strip  the  leaves  from  the  vines.  The  adults 
are  known  as  humming  bird  moths  because  of  their  large  size  and 
swift  flight.  They  are  gray  with  yellow  spots  on  the  sides  of  the 
body  and  have  a  wing  expanse  of  4  or  5  inches.  The  caterpillars 
may  be  controlled  by  hand  picking,  i.e.,  cutting  the  worms  in  two  with 
a  pair  of  scissors,  or  by  dusting  the  vines  with  1  part  of  powdered 
arsenate  of  lead  to  4  parts  of  finely  ground  hydrated  lime. 

WALNUT 

Blight,  Pseudomonas  juglandis  Pierce. — Young  tender  parts  are 
attacked.  Spots  at  first  watery,  soon  turning  black,  often  spread  and 
kill  young  nuts,  leaves,  or  tender  tips  of  shoots.  No  specific  remedy. 
Give  the  trees  the  best  possible  care.  Thin  out  the  tops  of  the  old  trees. 
Control  aphis.     Plant  resistant  varieties. 

Crown  Gall,  Wood  Decay,  Armillaria. — See  " General  Subjects." 

Melaxuma,  Dothiorella  gregaria  Sacc. — Black  sunken  cankers  de- 
velop on  larger  limbs  and  trunks;  the  limb  may  be  girdled  and  the 
part  above  die.  Cut  out  diseased  bark  areas  and  apply  Bordeaux 
paste. 

Winter  Killing. — Irrigate  about  November  1,  if  no  good  rains  have 
fallen.  Whitewash  trunks  in  the  fall.  Do  not  irrigate  after  August, 
except  as  above. 

Codling  Moth,  Cydia  pomonella  (Linn.). — See  "Apple."  This 
worm  feeds  on  the  green  husks  or  usually  bores  directly  into  the  kernel 
of  the  walnuts  before  they  are  mature,  and  also  often  works  its  way 


52  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

into  the  kernel  after  the  shell  becomes  hardened  by  making  an  en- 
trance in  the  suture  at  the  base.  It  may  be  controlled  by  spraying 
with  basic  arsenate  of  lead  or  by  dusting  with  powdered  basic  arsenate 
of  lead  and  hydrated  lime  when  work  on  husks  of  nuts  is  first  observed 
in  the  spring — May,  June,  or  July — depending  upon  climatic  condi- 
tions due  to  location  near  the  coast  or  inland.  Consult  local  horti- 
cultural officials. 

Frosted  Scale,  Lecanium  pruinosum  Coq.,  and  Cherry  or  Calico 
Scale,  L.  cerasorum  Ckll. — Same  control  as  for  brown  apricot  scale. 
See  "Apricot." 

Indian  Meal  Moth. — Attacks  walnuts  in  storage.     See  "Prune." 

Nautical  Borer,  Xylotrechus  nauticus  Mann. — The  borers  are  small, 
fleshy,  white  or  yellowish  grubs,  with  slightly  enlarged  anterior  end, 
and  about  three-quarters  inch  long.  The  adult  beetles  are  one-half 
inch  long,  dark  with  narrow  broken  yellow  or  whitish  cross  bands  on 
the  elytra.  The  larvae  work  in  the  small  twigs,  limbs,  and  trunks  of 
both  healthy  and  sickly  trees.  Cut  out  and  burn  all  infested  portions. 
Destroy  all  dead  oaks  or  prunings  in  the  neighborhood  to  eliminate 
breeding  places. 

Red  Humped  Caterpillar. — See  "Prune." 

Two-Spotted  Mite. — See  "Prune."  Dust  thoroughly  with  dry 
sulfur. 

Walnut  Aphis,  Chromatins  juglandicola  (Kalt.). — A  small  pale 
yellow  aphis  occurring  in  great  numbers  on  the  under  sides  of  the 
leaves  and  producing  great  quantities  of  honey  dew,  which  causes 
severe  smutting  of  the  foliage.  Dust  thoroughly  with  a  2  per  cent 
nicodust  during  last  week  of  May  or  the  first  part  of  June.  Some- 
times a  second  application  is  necessary  in  July  or  August. 

Walnut  Blister  Mite,  Eriophyes  erinea  Nalepa. — A  microscopic 
mite  producing  yellow  or  brown  felt-like  galls  on  the  under  sides  of 
the  leaves.  It  is  not  a  serious  pest,  but  may  be  cleaned  up  by  spraying 
trees  with  lime-sulfur  1-10  in  the  spring  when  the  buds  are  swelling. 
Control  measures  are  not  recommended  except  in  extreme  cases. 

Yellow-Necked  Caterpillar,  Datana  ministra  Drury. — A  black, 
hairy  caterpillar  with  numerous  longitudinal  yellow  stripes  on  the 
back  and  sides  and  a  yellow  or  orange-colored  neck.  It  averages  about 
two  inches  in  length  and  is  closely  related  and  similar  in  habits  to  the 
red-humped  caterpillar,  and  may  be  handled  in  the  same  way.  See 
same  under  "Prune." 

WATERMELON.     See  "Melon" 
WHEAT.     See  "Grain" 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  53 


GENERAL  SUBJECTS 


ARMILLARIA  ROOT  ROT  (OAK  FUNGUS),  Armillaria  mellea 

(Vahl)   Quel. 

Caused  by  a  native  fungus  which  lives  saprophytically  and  para- 
sitically  in  roots  of  woody  plants.  Trees  and  bushes  are  killed  in 
spots,  which  enlarge  year  after  year.  Affected  trees  fail  gradually 
from  diseased  side  or  die  suddenly  in  summer.  Under  the  affected 
bark  of  roots  there  is  a  yellowish  white  fan-shaped  mycelium  which 
progresses  into  live  bark.  Black  shining  root-like  strings  (rhizo- 
morphs)  grow  out  from  old  rotting  roots.  The  wood  decays  with  a 
uniform  white  rot.  Large  tan-brown  toadstools  (edible  when  cooked) 
arise  from  old  infections,  October  to  February.  Surgery  as  in  crown 
gall  or  pear  blight  can  sometimes  be  practiced  on  roots  and  crowns 
of  trees  not  too  far  gone.  Black  walnut,  French  pear,  and  fig  roots 
are  practically  immune.  Myrobalan  is  more  resistant  than  most  stone 
fruits  and  something  may  be  gained  by  working  high  on  this  stock. 
Similarly  the  Delicious  apple  on  its  own  roots  is  being  tried,  especi- 
ally for  Gravenstein,  which  seems  to  be  unusually  susceptible. 
Annual  fibrous  rooted  plants  are  rarely  injured.  Affected  areas 
in  orchard  may  be  isolated  by  opening  a  trench  3  to  4  feet  deep 
around  them.  This  may  be  filled  immediately  if  reopened  every  two 
years  to  keep  the  roots  cut  off.  Nursery  should  not  be  planted  in  in- 
fected soil. 

ARMYWORMS  AND  CUTWORMS 

General  Life  History. — The  adult  members  of  this  family  Noc- 
tuidae)  are  practially  all  night-flyers.  The  caterpillars  of  many  are 
known  as  armyworms  and  cutworms  and  are  among  the  most  destruc- 
tive of  insect  pests.  They  often  advance  from  field  to  field  in  great 
numbers,  like  an  army,  devastating  as  they  go.  Like  the  grasshoppers, 
they  attack  practically  all  kinds  of  plants,  including  field  and  truck 
crops,  vineyards  and  orchards,  as  well  as  flowers  and  weeds. 

The  adults  lay  their  eggs  in  spring  and  the  larvae  become  exceed- 
ingly numerous  in  early  summer,  when  most  of  the  damage  is  done. 
The  pupal  stage  is  passed  under  ground,  the  light  or  dark  brown  naked 
chrysalids  being  housed  in  small  earthen  cells.  There  are  several 
broods  a  year.  The  winter  is  usually  spent  in  the  pupal  stage,  but 
some  larvae  as  well  as  adults  hibernate.  A  hibernating  larva  often 
seriously  injures  grapevines  in  the  spring  by  eating  the  buds. 


54  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Control. — The  control  of  these  insects  has  been  a  difficult  problem 
for  years,  and  even  today  the  methods  worked  out  do  not  always  give 
relief. 

Clean  culture  in  fall  and  thorough  plowing  of  infested  fields  to 
kill  the  hibernating  pupae  in  the  cells  is  supposed  to  greatly  reduce 
the  next  year 's  broods.  This  has  been  recommended  as  especially  im- 
portant in  pea  fields  and  gardens. 

When  the  worms  begin  to  march  trenches  may  be  plowed  across 
and  ahead  of  their  paths  with  a  perpendicular  wall  in  front  of  the 
advance.  The  worms,  not  being  able  to  cross,  will  gather  in  great 
masses  in  these  trenches  and  can  be  easily  killed  by  spraying  with 
crude  oil  or  by  crushing  them  with  a  narrow  disk  or  roller.  Arsen- 
ical sprays  applied  as  soon  as  the  larvae  begin  to  appear  will  some- 
times materially  aid  in  protecting  crops  like  potatoes,  tomatoes,  young 
trees,  grapevines,  etc.,  but  are  seldom  practical  for  forage  crops. 

Poisoned  baits  (Formulas  4  and  5)  sown  in  the  infested  fields  will 
kill  countless  worms,  and  these  afford  by  far  the  most  satisfactory 
means  of  killing  these  insects  under  all  conditions.  In  fields,  pastures, 
orchards,  and  gardens,  the  poisoned  baits  may  be  freely  sown  over  the 
plants.  The  armyworms  and  cutworms  will  eat  the  bait  in  preference 
to  growing  vegetation. 

Light  traps  are  also  used  to  capture  the  adults,  but  these  have  never 
seemed  to  greatly  lessen  the  attacks,  because  large  numbers  of  the 
moths  captured  have  previously  laid  their  eggs. 

Natural  Enemies. — By  far  the  most  important  factors  in  the  con- 
trol of  armyworms  and  cutworms  are  natural  enemies.  The  parasitic 
tachinid  flies  kill  countless  numbers  of  them.  Hymenopterous  para- 
sites of  the  family  Ichneumonidae  also  prey  upon  the  young.  The 
predaceous  ground  beetles  of  the  family  Carabidae  devour  the  worms 
and  destroy  great  numbers.  That  armyworms  and  cutworms  are  not 
injurious  every  year  is  undoubtedly  due  to  the  work  of  these  natural 
enemies. 

CANKERWORMS 

Small  green  or  dark  measuring  worms  less  than  an  inch  long,  which 
feed  upon  the  leaves  and  young  fruit  and  drop  down  on  a  silken  thread 
when  the  tree  is  jarred.  The  females  are  wingless  and  crawl  up  the 
trees  in  the  fall  or  spring  to  lay  their  eggs  on  the  limbs  and  small 
branches.  Egg-laying  on  the  trees  is  prevented  by  placing  tanglefoot, 
cotton,  or  permanent  wire  screen  bands  around  the  trunks  of  the  trees 
in  the  fall  in  order  to  catch  both  the  fall  and  spring  forms.     The  cater- 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  55 

pillars  are  easily  jarred  from  the  trees,  but  will  crawl  up  again  if  not 
obstructed.  Spraying  with  arsenate  of  lead  (Formula  4)  will  also 
give  control. 

CROWN  GALL,  Bacterium  tumefaciens  S.  &  T. 

Rounded  fleshy  to  woody  tumors  form  on  roots  or  sometimes  on 
above-ground  parts,  usually  starting  from  wounds,  persisting  and 
growing  at  the  edges  from  year  to  year,  often  girdling  or  causing  the 
tree  to  break  off.  For  nurseries,  avoid  old  vineyard,  orchard,  or  berry 
land  which  has  been  seriously  infected.  Throw  out  all  affected  nurs- 
ery trees.  The  clean  trees  in  a  lot  having  a  large  percentage  affected 
are  of  doubtful  value.  In  orchards,  occasionally  examine  crown  and 
main  roots,  especially  of  stunted  trees.  When  not  too  far  advanced 
this  disease  may  be  controlled  by  chiseling  out  the  galls,  removing 
all  abnormal  tissue  to  healthy  bark  and  down  to  sound  wood,  steriliz- 
ing with  corrosive  sublimate  (Formula  28  or  28a),  and  covering  the 
wounds  with  Bordeaux  paste  or  asphaltum.  The  trees  must  be  gone 
over  again  after  vigorous  growth  has  been  going  on  for  several  weeks 
and  the  new  galls  which  arise  at  the  wound  margins  treated.  Rein- 
spection  is  essential.  Badly  affected  and  stunted  trees  should  be 
pulled  out  and  replanted,  using  fresh  soil. 

DAMPING-OFF 

Young  seedlings  rot  at  or  below  the  surface  of  the  ground  and  fall 
over  or  wilt.  Many  may  die  before  emerging.  Cause,  various  soil 
fungi,  Pythium,  Rhizoctonia,  Fusarium,  and  others.  Best  controlled 
by  skill  in  watering.  Water  the  plant  beds  only  in  the  morning  and 
on  bright  days.  Do  not  sprinkle  oftener  than  necessary.  In  green- 
houses or  frames  give  plenty  of  ventilation.  In  making  citrus  seed 
beds  put  an  inch  or  two  of  dry  sand  on  the  top  of  the  soil.  Some 
forms  of  damping-off  may  be  prevented  by  soil  disinfection.  See 
p.  95.  Where  damping-off  has  started,  spraying  the  plants  and 
ground  with  Bordeaux  may  do  some  good. 

FROST  AND  COLD  INJURY 

With  yonug  citrus  trees  in  frosty  localities,  wrap  the  trunks  with 
corn  or  milo  stalks  in  winter.  Heap  up  earth  around  the  butts.  En- 
close tender  valuable  young  trees  with  burlap  covers.  For  bearing 
groves  obtain  detailed  information  about  methods  and  appliances  for 
smudging  with  oil  fuel.  (See  also  Sour  Sap.)  Many  plants  are  in- 
jured and  disfigured  by  cold  at  critical  stages  of  development,  even 
when  it  is  not  cold  enough  to  kill  or  even  noticeably  injure  them  at 
the  time. 


56  UNIVERSITY    OP    CALIFORNIA — EXPERIMENT    STATION 


GRASSHOPPERS 

Scatter  poison  bran  mash  or  citrus  bran  mash  freely  (Formula  4 
or  5).  Be  sure  to  mix  the  bran  and  poison  thoroughly.  Scatter  in 
alfalfa  fields  about  4  o'clock  in  the  afternoon  and  around  orchard 
trees  or  other  plants  early  in  the  morning. 

GUMMOSIS 

Gum  formation  in  itself  is  not  due  to  any  one  specific  disease,  but 
may  be  brought  about  by  many  different  causes.  In  stone  fruit  and 
citrus  trees  gumming  is  simply  a  symptom  of  distress,  which  may  be 
due  to  specific  infections  or  various  other  causes,  such  as  unsuitable 
soil,  poor  condition  of  soil,  sunscald,  excess  or  lack  of  water,  frost, 
or  attacks  of  parasites.  Treatment  must  vary  according  to  cause. 
Badly  gummed  branches  may  be  removed,  gummy  diseased  areas  of 
bark  cut  out,  and  the  wounds  treated  as  in  citrus  gummosis.  Splitting 
the  bark  is  useless  and  often  harmful. 

NEMATODE  (EEL  WORM) 

Microscopic  worms  of  several  species  penetrate  the  tender  tissues 
of  plants.  The  garden  nemotode  (Heterodara  radicicola  Greef.)  causes 
rounded  irregular  fleshy  swellings  or  root  knots  on  tender  roots.  If 
abundant,  the  roots  may  become  much  distorted  and  swollen,  growth 
stops,  and  early  rotting  off  follows. 

Do  not  attempt  to  grow  susceptible  crops  on  infested  soil.  Keep 
such  areas  clean  cultivated  in  summer  or  in  a  cereal  crop.  Grain  may 
be  grown  in  winter.  Almost  all  important  crops,  except  cereals  and 
some  fruit  trees,  are  attacked  by  the  garden  nematode.  The  beet 
nematode  (H.  schactii  Schmidt)  attacks  some  other  plants,  and  where 
it  occurs  careful  rotations  should  be  followed  with  total  exclusion  of 
beets  for  many  years.  Alfalfa  is  not  seriously  affected  by  the  com- 
mon species,  but  carries  it  over  to  future  crops.  Alfalfa  may  be 
safely  planted  on  beet  nematode  soil.  Nematodes  are  worse  on  sandy 
soils. 

Soil  intended  for  greenhouse  use  should  be  taken  from  places 
where  nematodes  do  not  occur.  The  absence  of  nematodes  is  best 
determined  by  examining  growing  plants  such  as  figs,  peaches,  melons, 
tomatoes,  or  nearly  any  soft-rooted  vegetables.  Where  it  is  not  possi- 
ble to  get  soil  which  is  certainly  free,  it  should  be  sterilized.  See 
p.  95. 

Nematodes  are  frequently  distributed  in  potatoes  and  rooted 
plants. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  57 


PHYSIOLOGICAL  DISEASES 

(Little  Leaf,  Exanthema,  Die-Back,  Mottled  Leaf,  Rosette,  Bitter  Pit, 
Dry  Rot,  Blossom-End  Rot) 

Diseases  of  a  specific  nature  of  which  the  cause  is  not  known  and 
of  which  the  symptoms  seem  unlike  the  usual  effects  of  unfavorable 
conditions  or  parasites.  Most  of  these  troubles  show  a  relation  to  soil 
conditions  and  occur  especially  in  dry,  sandy,  gravelly,  or  hardpan 
soils,  those  very  deficient  in  humus,  or  under  conditions  of  irregular 
soil  moisture.  Trees  standing  over  old  barnyards  or  corrals  or  where 
excessive  amounts  of  manure  have  been  applied  are  also  likely  to  show 
some  of  these  troubles.  The  most  promising  methods  of  treatment  are 
increasing  the  humus  content  of  the  soil  by  means  of  green  manure 
crops  and  mulches,  breaking  up  all  hardpan  and  plow-soles,  more  care- 
ful irrigation  to  insure  the  maintenance  of  a  proper  and  uniform 
moisture  condition  of  the  soil  down  to  a  depth  of  several  feet  and 
throughout  the  season  until  rains  occur,  and  planting  alfalfa  in  orch- 
ards where  plenty  of  water  is  available.  The  soil  in  areas  where  these 
troubles  occur  should  be  examined  for  alkali  or  other  injurious  sub- 
stances. Where  any  of  these  diseases  are  serious  and  persistent  it  may 
be  better  to  grow  some  other  crop  than  to  keep  on  with  one  which  is 
seriously  affected. 

SLUGS  AND  SNAILS 

May  be  controlled  to  some  extent  by  thoroughly  dusting  finely 
powdered  hydrated  lime  over  the  infested  plants,  but  recent  investi- 
gations have  shown  that  a  5  per  cent  nicodust  is  very  effective  in  kill- 
ing these  pests  if  applied  late  in  the  evening  or  on  dull  days  when  the 
animals  are  at  work  on  the  plants.  Trapping  by  means  of  boards  or 
wet  sacks  and  killing  those  taking  shelter  thereunder  is  effective  in  a 
small  way. 

SOUR  SAP,  WINTER  INJURY.     Also  see  ' '  Sunburn ' ' 

All  the  ordinary  forms  of  sour  sap  are  due  to  extreme  variations  in 
temperature.  Differences  in  the  effect  upon  individual  trees  or  orch- 
ards are  due  to  differences  in  condition  and  susceptibility  of  the  trees, 
produced  mostly  by  variation  in  the  moisture  condition  of  the  soil. 
Do  not  force  growth  late  in  summer.  Irrigate,  if  possible,  about  No- 
vember 1,  if  no  heavy  rain  has  fallen.  Whitewash  bodies  of  trees 
early  in  November.     Sour  sap  seems  to  be  associated  with  hardpan 


58  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

or  periods  of  surplus  water  in  the  soil.  Good  drainage  should  be 
emphasized.  A  furrow  may  be  opened  in  early  winter  on  either  side 
of  the  tree  row  to  carry  off  surplus  winter  rains  and  prevent  the 
soil  from  remaining  saturated  for  prolonged  winter  periods.  Num- 
erous instances  have  been  observed  where  open  irrigation  ditches 
have  drained  adjacent  tree  rows  during  the  winter.  Trees  in  the 
drained  soil  have  escaped  sour  sap  while  those  farther  from  the  ditch 
in  soil  saturated  with  winter  water  have  suffered  badly. 

Wood  Decay  Prevention,  Treatment  of  Pruning  Cuts  and  Wounds. 
— It  is  doubtful  whether  any  application  on  wounds  materially  assists 
healing  except  for  some  delicate  plants  like  roses,  where  the  cut  stem 
may  dry  out.  Treatment  is  to  prevent  infection  with  spores  of  wood 
decay  fungi,  which  may  be  carried  by  wind,  rain  or  otherwise,  and  be 
protected  in  cracks  or  rough  places  in  dry  wood  or  bark  until  moist 
weather,  when  they  grow  and  penetrate  the  wood,  causing  rot.  At 
some  seasons  bark  knocked  off  may  be  renewed  over  the  whole  surface 
if  undisturbed,  or  the  bark  may  be  replaced  and  held  firmly  and  again 
grow  on.  Usually  a  wound  must  heal  from  the  edges.  The  greatest 
danger  comes  from  cracks  in  the  heartwood,  from  rough  breaks  and 
from  the  "heel"  at  the  bottom  of  a  bad  cut  in  which  the  bark  nearly 
always  dies  back.  Proper  training  of  trees  from  the  beginning  to 
avoid  narrow  pinching  joints  and  subsequent  splitting  is  important. 
Treatment  should  be  prompt,  since  when  decay  is  established  no  dis- 
infectant can  be  expected  to  penetrate  far  enough  to  destroy  the 
active  fungus  in  the  wood.  Make  a  clean  cut,  trimming  the  bark 
down  smoothly  to  sound  tissues  around  the  edges.  In  the  case  of 
branches,  make  a  close  cut,  leaving  no  projecting  stub.  Thoroughly 
cover  the  wound  with  Bordeaux  paste  (Formula  10),  and  when  well 
dried  cover  with  grade  D  asphaltum  put  on  in  a  melted  condition. 
Go  over  the  work  occasionally,  especially  in  summer  or  early  fall, 
and  renew  the  application  of  asphaltum  until  the  wound  is  entirely 
healed.  Bordeaux  mixture  may  retard  the  formation  of  callus.  Some 
prefer  to  paint  the  whole  wound  at  once  with  hot  asphaltum.  Others 
prefer  to  use  the  asphalt  paint  cold,  but  this  should  be  done  with 
care  to  keep  cracks  in  the  wood  thoroughly  covered.  Some 
asphaltums,  especially  the  cold  paints,  have  caused  injury.  Where 
wounds  have  stood  for  some  time  before  covering,  it  would  be  well 
to  wet  the  dry  wood  with  a  solution  of  corrosive  sublimate,  1  part 
in  500  parts  of  50  per  cent  alcohol  (V4  ounce  in  1  gallon).  See  p.  90 
for  precautions  in  using  corrosive  sublimate. 

For  tree  surgery  methods,  send  to  Superintendent  of  Documents, 
Washington,  D.  C,  for  Farmers'  Bulletin  No.  1178,  price  25  cents. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  59 


SUNBURN 

Whitewash  bodies  in  fall  as  well  as  spring.  Shape  the  trees  so  that 
their  trunks  are  shaded.  Cut  young  trees  back  well  before  planting. 
Shade  trunks  with  shakes  or  protectors.  Do  not  allow  trees  to  suffer 
from  drought. 

Tests  show  that  the  coloring  matter  in  the  bark  of  the  trunk  and 
exposed  main  limbs  absorbs  heat  enough  on  sunny  days  in  winter  to 
raise  the  temperature  of-  the  growing  layer  35°  to  40°  F.  above  the 
temperature  of  the  air.  As  soon  as  the  sun  goes  down  the  tree  cools 
rapidly  to  atmospheric  temperature,  which  may  be  freezing  or  below. 
Whitewash  reflects  the  heat,  so  that  the  growing  layer  does  not  get 
warmer  than  the  air ;  the  cells  remain  dormant  during  the  day,  and  are 
not  injured  by  low  temperatures  at  night.  The  above  also  applies  in 
opposing  sour  sap. 

TENT  CATERPILLARS 

Gray  or  brown,  hairy  caterpillars  with  row  of  white  spots  on  back 
or  pale  bluish  lines  on  sides,  measuring  from  1  to  3  inches  long.  They 
either  live  in  compact  colonies  or  in  tightly  woven  webs  or  tents  which 
are  conspicuous  on  the  trees.  Entire  colonies  may  be  exterminated  by 
cutting  off  or  burning  with  a  torch.  Those  on  the  trunks  and  large 
limbs  may  be  killed  by  spraying  with  kerosene  or  concentrated  oil 
emulsions.  The  small  dark  egg  masses  encircling  the  smaller  limbs 
may  be  pruned  out  when  the  trees  are  dormant  and  burned.  Spraying 
with  arsenate  of  lead  (Formula  1  or  2)  will  control  the  caterpillars 
effectually. 

WIREWORMS 

Wireworms  get  their  name  from  their  smooth,  round  bodies,  which 
are  usually  shiny,  varying  in  color  from  pale  yellow  to  dark  brown. 
The  common  injurious  forms  are  about  one  inch  long.  They  live  in 
the  soil,  preferring  sandy  loams  rather  than  heavy  soils,  although  they 
may  be  found  in  either.  The  larval  stages  last  from  1  to  3  years,  so 
that  to  be  effective  control  measures  must  cover  the  maximum  period. 
The  adult  beetles  are  known  as  ' '  click  beetles ' '  because  of  their  ability 
to  jump  in  the  air  with  a  clicking  sound.  They  are  mostly  inconspicu- 
ous beetles  of  various  shades  of  brown  or  entirely  black,  about  one- 
half  inch  long.    They  are  active  and  fly  freely. 

Control  measures  are  difficult  because  of  the  underground  habits 
of  the  larvae,  and  as  yet  have  not  been  satisfactorily  worked  out  for 
the  different  species.     Clean  culture  and  crop  rotations  are  the  most 


60  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

reliable  practices,  while  much  good  comes  from  thorough  cultivation. 
Trapping  the  adults  with  small  piles  of  straw  and  burning  them  in  fall 
and  winter  destroys  large  numbers.  Replanting  is  often  necessary 
with  many  crops  such  as  potatoes,  beans,  peas,  melons,  etc.  Some  con- 
trol is  claimed  from  scattering  poison  bran  mash  (Formula  4)  over  the 
surface  of  the  ground. 

HOUSEHOLD  PESTS 
AND  ANIMAL  PARASITES 

Ants. — Ants  are  not  only  serious  household  pests  but  do  harm 
in  the  garden  and  orchard  by  distributing  plant  lice,  scale  insects, 
and  other  honeydew  producing  insects,  and  protecting  them  from 
parasitic  enemies,  which  would  otherwise  destroy  great  numbers  of 
these  pests. 

The  ordinary  small  house  ants,  which  give  off  a  pungent  char- 
acteristic "ant"  odor  when  crushed,  are  best  controlled  by  using 
various  strong  arsenic  and  syrup  poisons  sold  as  ' '  ant  poisons. ' '  The 
Argentine  ant,  which  gives  off  no  characteristic  odor,  is  controlled 
by  a  very  weak  arsenate  and  syrup  poison  which  is  carried  to  the 
young  by  the  workers  and  which  gradually  kills  out  the  whole  colony. 
For  this  pest  use  Formula  7  or  8,  or  buy  special  Argentine  ant  poison. 

Home-made  containers  for  the  latter  poison  may  be  made  by  punch- 
ing small  holes  around  the  tight-fitting  tops  of  cans  and  then  dipping 
in  hot  paraffine  to  prevent  rusting.  A  sponge  is  placed  in  the  bottom 
and  thoroughly  wet  with  the  poison,  the  lid  is  securely  fastened,  the 
container  marked  ' '  Poison ' '  and  then  hung  up  under  or  in  the  house, 
or  in  the  gardens  or  orchards,  away  from  the  reach  of  children.  Small 
fruit  jars  with  holes  punched  in  the  lids  may  be  used  instead  of  cans, 
and  if  screwed  very  tightly  are  less  likely  to  be  opened  by  children. 

Bed  Bugs. — These  insects  lay  their  eggs  in  cracks  and  crevices 
about  the  furniture  and  room.  They  will  withstand  months  of  starva- 
tion. Heating  the  rooms  infested  to  120°  F.  for  12  to  24  hours  is 
a  satisfactory  method  of  control  where  practical.  Fumigation  with 
cyanid  is  effective.  Careful  washing  with  corrosive  sublimate  1-500 
(1  ounce  to  4  gallons  of  water)  of  all  objects  and  crevices  is  a 
substitute  if  the  other  methods  cannot  be  used.  Care  should  be 
taken  not  to  wet  the  hands  or  body  in  solutions  of  this  strength. 
Live  steam  if  available  is  effective  when  applied  to  bunks,  crevices,  etc. 

Cockroaches. — Can  best  be  controlled  by  mixing  sodium  fluorid 
(commercial)  with  flour  in  equal  proportion  and  scattering  it  heavily 
along  the  shelves  or  corners  frequented  by  the  insects. 


Circular  265]  PLANT  DISEASE  AND  FEST  CONTROL  61 

Clothes  Moths. — These  insects  damage  fur  and  woolen  goods  by 
the  feeding  of  their  larvae.  Careful  brushing  and  airing  of  stored 
materials  at  frequent  intervals  is  the  best  protection  for  garments 
infrequently  used.  If  stored  over  long  periods,  they  should  be  care- 
fully brushed,  placed  in  tight  boxes  and  the  covers  sealed  with  gummed 
paper.  Fumigation  with  carbon  bisulfid  or  carbon  tetrachlorid  is 
effective  in  heavily  infested  quarters.  Moth  balls,  cedar  chests,  etc., 
are  effective  but  will  not  kill  larvae  that  are  already  present  in  the 
materials. 

Fleas. — The  presence  of  fleas  is  closely  correlated  with  the  presence 
of  domestic  animals  or  pets.  They  lay  their  eggs  on  these  hosts. 
There  hatches  from  these  eggs  which  have  dropped  to  the  ground 
or  floor,  a  maggot-like  larva  which  lives  on  nitrogenous  material  until 
it  changes  into  a  mature  flea.  Domestic  pets  should  be  frequently 
dusted  with  fresh  pyrethrum  powder  or  washed  in  heavy  suds  of 
naptha  soap.  Mats  should  be  provided  for  pets  to  sleep  on  if  per- 
mitted in  the  house  and  these  regularly  shaken  over  an  open  fire.  All 
animals  should  be  excluded  from  the  basement.  Floors  should  be 
mopped  with  "dry"  mops  moistened  in  kerosene.  Napthalene  flakes 
spread  over  the  floor  of  a  room,  allowed  to  remain  for  a  few  hours 
and  then  brushed  into  another  room  prove  effective  in  severe  out- 
breaks.    For  sticktight  flea  see  Circ.  251. 

Flies. — Life  History. — The  common  house  fly  lays  its  eggs  on 
freshly  deposited  manure  heaped  in  piles,  also  on  heat-producing 
piles  of  vegetables  and  animal  matter.  These  hatch  in  about  two 
days  into  tiny  glistening  white,  footless  maggots  that  grow  rapidly 
for  approximately  a  week  until  about  half  an  inch  in  length,  when 
they  migrate  from  the  moister  part  of  the  manure  to  a  drier  portion ; 
here  they  turn  into  brown,  barrel-shaped  "pupae,"  from  which  they 
emerge  as  full-grown  flies  in  about  four  days. 

The  blow  flies,  flesh  flies,  buzz  flies,  or  meat  flies,  as  they  are 
variously  called,  will  also  breed  in  manure  and  garbage,  but  prefer 
the  bodies  of  dead  animals  left  exposed  on  the  ground  or  buried  in 
shallow  holes. 

When  garbage  is  fed  to  animals  or  left  exposed,  unless  extra  pre- 
cautions are  taken,  fly  breeding  will  occur  in  the  garbage  itself  and 
even  in  moist  soil  that  has  become  saturated  with  liquid  food  material, 
urine  and  feces. 

Manure  should  be  removed  at  intervals  of  less  than  one  week 
and  spread  out  in  a  layer  sufficiently  thin  to  cause  immediate  drying. 
If  it  must  be  kept  on  the  premises  for  longer  periods  it  should  be  stored 
in  fly-tight  bins  or  composted  in  neat,  clean-edged  piles. 


62  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Dead  animals  should  be  incinerated  or  if  buried  the  carcasses 
should  be  liberally  sprinkled  with  lime  or  crude  oil  and  the  ground 
well  tamped. 

Flies  are  best  poisoned  inside  the  house  by  sweetened  2  per  cent 
solutions  of  formaldehyde  mixed  with  milk  and  exposed  in  saucers 
at  night  ready  for  flies  early  in  the  morning,  other  sources  of  water 
having  been  removed. 

The  larvae  may  be  destroyed  in  manure  by  sprinkling  the  pile 
with  borax  at  the  rate  of  %  pound  to  10  cubic  feet  of  manure  and 
following  this  application  with  enough  water  to  carry  the  borax  at 
least  six  inches  into  the  mass.  Repeated  borax  treatment  will  make 
such  manure  injurious  to  plants  if  used  as  a  fertilizer. 

Mosquitoes. — These  insects  should  be  attacked  in  their  breeding 
places,  standing  water,  all  accumulations  of  which  should  be  drained 
or  the  depressions  filled.  If  this  is  not  practicable,  oiling  the  surface 
with  an  oil  made  of  equal  parts  of  crude  oil  and  kerosene  will  tem- 
porarily reduce  the  nuisance  but  must  be  repeated  at  intervals  of  two 
to  three  weeks.  Inasmuch  as  certain  mosquitoes  are  able  to  transmit 
malaria  from  one  person  to  another  care  should  be  taken  to  prevent 
their  entrance  to  living  quarters  by  screening  and  individual  capture 
if  they  succeed  in  gaining  entrance.  The  malaria-transmitting  species 
may  be  detected  by  their  habit  of  standing  with  the  head  pointing 
down  and  the  abdomen  raised  when  at  rest. 

Silver  Fish  Moth. — This  wingless  leaden  colored  insect  sometimes 
becomes  important  through  its  eating  starchy  materials  such  as 
laundered  sheets,  bookbindings,  wall  paper,  etc.  They  are  controlled 
by  use  of  a  bait  composed  of  10  parts  of  starch  to  1  part  of  white 
arsenic. 

Sow  Bugs. — These  crustaceans  migrate  indoors  at  the  beginning 
of  each  rainy  season.  Damp  cloths  placed  under  a  board  at  night 
outside  the  buildings  or  in  basements  collect  large  numbers  which 
may  be  destroyed  by  soaking  the  cloth  with  hot  water,  kerosene  or 
gasoline. 

(See  also  Poison  Baits,  Formulas  4  and  5,  p.  72.)  Sliced  potatoes 
or  carrots  sprinkled  with  Paris  green  or  white  arsenic  often  give  good 
control  if  placed  where  the  sow  bugs  are  numerous. 

Tule  Bugs  or  Stink  Bugs. — These  bugs  cause  great  annoyance  by 
entering  houses  often  in  great  numbers  in  search  of  shelter  in  the 
autumn  time  when  they  are  driven  by  the  rains  from  the  lowlands 
where  they  breed  and  feed  on  other  insects  along  the  river  margins 
and  in  moist  places.     Once  in  the  house  they  are  hard  to  get  rid 


CIRCULAR  265]  PLANT  DISEASE  AND  PEST  CONTROL  63 

of  especially  if  the  house  is  moist,  but  a  well-warmed  and  dry  house 
does  not  serve  them  well.  Keeping  doors  and  windows  well  screened 
and  all  cracks  closed,  particularly  when  lights  are  burning  will  help 
considerably  in  keeping  them  out  when  they  are  making  their  nights. 
The  invasions  are  only  temporary. 

CATTLE 

Ear  Ticks — Ornithodorus  megnini  Duges — This  tick  lives  its  entire 
life  within  the  auditory  canals  of  the  ears  of  domesticated  animals,  par- 
ticularly cattle,  except  when  it  leaves  to  deposit  its  eggs  in  the  ground. 
The  young  ticks  hatching  from  these  eggs  crawl  on  the  bodies  of  avail- 
able animals  and  enter  the  ears.  Control  must  be  by  individual  treat- 
ment. The  application  of  a  half-and-half  mixture  of  cottonseed  oil 
and  pine  tar  in  quantity  sufficient  to  fill  the  auditory  canal  is  very 
effective. 

Horn  Flies  Haematobia  serrata  R.  D. — These  flies,  about  one-half 
the  size  of  the  common  house  fly  cluster  about  the  rump  and  head  of 
cows,  sucking  blood  and  constituting  a  serious  nuisance  in  the  case  of 
dairy  cattle.  They  deposit  their  eggs  on  the  freshly  deposited  cow 
manure.  The  young  maggots  live  in  this  material  until  ready  to 
change  to  an  adult  fly,  when  they  burrow  into  the  surrounding  earth 
to  pupate.     The  life  history  lasts  from  10  to  16  days. 

Corrals  should  be  cleaned  of  manure  weekly  or  dragged  with 
a  heavy  brush  drag  daily  to  break  up  the  clots  of  manure  and  thus 
dry  them  out. 

Biting  Lice,  Trichodectes  scalaris  Nitzsch. — The  biting  louse  may 
be  differentiated  from  the  sucking  louse  by  its  round  head  and  the 
fact  that  it  is  never  found  with  its  mouth  parts  imbedded  in  the 
animal's  flesh.  It  may  be  controlled  by  one  dusting  with  sodium 
fluoride  (commercial)  mixed  with  flour  in  even  proportions,  or  by 
dipping,  spraying,  or  bathing  with  a  coal  tar  dip  (Formula  266)  at 
intervals  of  ten  days. 

Sucking  Lice. — These  lice  suck  the  blood  of  the  animals  and  may 
be  distinguished  from  the  biting  lice  by  their  pointed  heads  and  the 
fact  that  they  are  generally  found  with  their  mouth  parts  plunged 
into  the  animal's  flesh.  Sodium  fluoride,  so  successful  for  the  biting 
lice,  is  useless  against  this  class  of  lice.  Coal  tar  dips  applied  as  a  dip 
or  spray  or  rubbed  on  are  effective  but  must  be  repeated  at  the  expira- 
tion of  ten  days  to  be  successful.  Raw  linseed  oil  applied  with  a  brush 
at  intervals  of  a  week  will  also  control  both  types  of  lice. 


64  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Lungworms,  Dictyocaulus  viviparus  Bloch. — These  worms  are 
parasitic  in  the  air  passages  of  the  lungs.  The  eggs  containing  living 
young  are  coughed  up  and  swallowed,  hatch  out  in  the  small  intestine, 
and,  after  spending  a  period  outside  the  body  are  taken  in  again  with 
food  or  water,  and  after  penetrating  the  small  intestine  are  borne 
back  to  the  lungs.  They  cause  serious  damage  by  causing  a  collapse 
of  those  portions  of  the  lung  from  which  the  air  supply  is  shut  off 
by  the  blocking  of  the  bronchioles,  thus  forming  a  favorable  medium 
for  the  growth  of  pathogenic  organisms  that  may  actually  cause  the 
death  of  the  infected  animals.  Chloroform  injected  into  the  nostrils 
in  quantities  sufficient  to  make  the  animals  slightly  groggy,  often  kills 
large  numbers  of  the  lungworms  and  greatly  facilitates  recovery. 
(See  "Sheep"  regarding  the  danger  of  chloroform  treatment  with 
this  animal.)  Sufficient  food  and  proper  shelter  are  very  important. 
Infection  is  incurred  in  moist,  swampy  localities.  Wherever  possible 
such  areas  should  be  eliminated  from  the  range  or  fenced  off  and 
drinking  water  supplied  in  troughs  high  enough  to  avoid  contam- 
ination with  feces. 

Ticks. — Various  ticks  attack  the  bodies  of  cattle.  Where  these 
occur  in  large  numbers  or  where  the  tick  concerned  is  the  Texas 
Fever  Tick,  Margaropus  annulatus  Say,  which  may  be  recognized  by 
its  chestnut-colored  shield  and  the  fact  that  its  first  pair  of  legs 
originates  on  the  "shoulders"  and  not  close  to  the  shield,  measures 
should  be  taken  for  control.  Dipping  in  an  arsenical  dip  (Formula 
3a)  is  most  satisfactory.  Where  only  a  few  animals  are  concerned, 
spraying  may  be  substituted  for  the  dipping. 

Warbles,  Hypoderma  lineata  de  Villers. — These  maggots  which 
cause  the  lumps  or  swellings  on  the  backs  of  cattle  are  the  larvae 
of  a  fly  resembling  a  bee  which  deposits  its  eggs  on  the  heels  or  legs 
of  cattle.  On  hatching  these  maggots  bore  into  the  skin  and  penetrate 
to  their  position  on  the  back  beneath  the  skin.  When  about  ready  to 
change  to  a  fly  a  hole  appears  above  the  maggot  which  is  used  for  its 
exit.  It  then  falls  to  the  ground,  burrows  into  the  earth  for  two  or 
three  inches  whence  it  emerges  in  about  three  weeks  as  a  full-grown  fly 
ready  to  deposit  eggs  on  other  cattle.  The  control  is  individual  in  that 
the  maggot  when  "ripe"  must  be  forced  out  of  the  lumps  on  the  back 
and  destroyed.  Care  should  be  taken  not  to  crush  the  warble  in  the 
wound  for  such  accidents  sometimes  produce  serious  poisoning.  If 
this  happens  the  wound  should  be  carefully  washed  out  with  water  to 
which  salt  at  the  rate  of  two  teaspoonfuls  to  the  pint  has  been  added. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  65 


SHEEP 

,  Head  Maggot,  Oestrus  ovis  Linn. — These  pests  are  the  larvae  of 
flies  that  deposit  their  eggs  on  living  young  near  the  nostrils.  The 
young  migrate  up  the  nasal  cavity  penetrating  to  the  sinuses  where 
they  are  often  trapped  by  their  growth  in  size.  Their  presence  may 
be  detected  by  the  attitude  of  the  infected  animal,  which  stands  head 
down  and  inclined  to  one  side  and  at  intervals  follows  the  inclination 
of  its  head  around  in  circles.  This  may  be  distinguished  from  ' '  gid ' ' 
by  the  fact  that  with  head  maggot  infestations  there  is  a  discharge 
from  the  nostrils.  Some  relief  may  be  had  by  causing  the  animals  to 
sniff  up  red  pepper,  the  larvae  being  discharged  by  violent  sneezing. 
Prevention  is  accomplished  by  the  use  of  "salt  logs"  made  by  boring 
2  to  3  inch  holes  in  a  log,  filling  the  cavities  with  salt  and  smearing  the 
circumference  of  the  holes  with  soft  tar.  The  animals  in  attempting 
to  get  the  salt  keep  their  muzzles  painted  with  tar  which  acts  as  a 
repellent. 

Lungworms,  Dictyocaulus  filaria  Rud. — See  "Cattle"  for  general 
consideration.  Little  can  be  clone  in  the  way  of  treatment  for  sheep 
affected  with  lungworms  as  they  are  very  susceptible  to  chloroform, 
which  consequently  cannot  be  used  for  these  animals.  Good  food  and 
comfortable  shelter  will  generally  accomplish  the  desired  end  although 
the  sanitary  precautions  should  not  be  overlooked. 

Scab. — This  disease  which  manifests  its  presence  by  the  ' '  tagging ' ' 
of  the  wool  and  crusting  of  the  underlying  skin  is  caused  by  a  micro- 
scopic mite,  Psoroptes  communis  var.  ovis.  Hering.  These  mites  punc- 
ture the  skin  causing  an  intense  itching;  the  roughening  of  the  skin 
and  eventually  a  crustiness  causes  the  wool  to  fall  out  or  ' '  tag. ' '  Con- 
trol is  by  means  of  dipping  in  lime-sulfur  dip  (Formula  17a).  Pastures 
which  have  been  used  for  infested  sheep  should  not  be  utilized  for 
clean  sheep  for  three  months  unless  drenching  rains  have  intervened. 

Wool  Maggots. — These  pests  are  the  larvae  of  flesh  flies  that, 
attracted  by  the  odor  of  soiled  wool,  attack  first  the  wool  and  later 
the  flesh  of  the  sheep.  The  points  of  attack  are  largely  confined  to 
the  area  about  the  hind  quarters  where  the  wool  becomes  soiled  with 
feces.  "Crutching, "  the  clipping  of  the  wool  around  the  anus  and 
inside  the  hind  legs,  helps  prevent  infestation.  Infested  flesh  should 
be  cleaned  of  maggots  by  the  application  of  sheep  dip  and  the  odor 
of  putrefaction  destroyed  by  formaldehyde  or  pine  tar  in  order  to 
prevent  further  infestation.  "Jetting"  of  the  hind  quarters  under 
100  pounds  pressure  with  sheep   dip  to  which   5  pounds  of  white 


66  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

arsenic  has  been  added  is  curative  and  acts  as  a  protection  for  from 
one  to  three  months.  The  bodies  of  dead  animals,  in  which  these 
flies  also  develop  in  enormous  numbers,  should  be  incinerated. 

DOGS 

Fleas. — See  " Household   Insects." 

Mange  or  Scabies. — See  "Sheep"  for  general  consideration. 
Sarcoptes  scabiei  var.  canis  Linn.  Treatment. — Affected  parts  should 
be  thoroughly  washed  with  warm  water  and  soap  until  the  skin  is  thor- 
oughly softened.  Sulfur  ointment  made  by  mixing  sulfur  and  lard 
should  be  carefully  rubbed  into  the  skin.  This  should  be  repeated 
every  five  days. 

Demodectic  or  Follicular  Mange  is  commonly  called  the  "Red 
Mange"  of  dogs.  It  is  caused  by  a  microscopic  elongated  mite  known 
as  Demodex  folliculorum  Simon  which  burrows  into  the  hair  follicles. 
The  chances  of  cure  are  slight  and  valuable  or  valued  dogs  should 
be  placed  under  the  care  of  a  skilled  veterinarian  where  facilities 
are  available  for  the  production  of  auto-vaccines.  Itchthyol  (10  per 
cent)  and  formalin  (5  per  cent)  are  both  highly  recommended. 

Roundworms,  Toxascaris  limbata  R.  &  H.  and  Belascaris  mar- 
ginata  Rud. — These  worms  normally  inhabit  the  small  intestine  but 
are  great  wanderers  and  are  often  found  in  the  stomach  which  accounts 
for  their  name  of  "maw"  worms.  The  eggs  are  ingested  with  food 
contaminated  by  the  feces  of  infested  dogs.  These  hatch  in  the 
stomach  and  the  larvae  penetrate  to  the  lungs,  into  the  air  spaces  of 
the  latter,  up  the  windpipe  and  down  the  esophagus  to  their  final 
resting  place  in  the  small  intestine.  This  migration  is  often  the 
cause  of  serious  pneumonic  difficulties  in  puppies. 

Control  is  by  administration  of  oil  of  chenopodium  at  the  rate  of 
1  c.c.  for  each  pound  of  body  weight  combined  with  a  dose  of  castor  oil. 

Tapeworms. — All  tapeworms  of  the  dog  have  an  intermediary  host, 
i.e.  another  animal  in  which  the  tapeworm  lives  and  which  must  be 
eaten  by  the  dog  in  order  to  infect  the  latter.  The  various  tapeworms 
of  dogs  find  their  intermediary  hosts  in  lice,  fleas,  rabbits,  and  sheep 
among  others.  The  commonest  tapeworm  of  dogs  is  Dipylidium  cani- 
num  Linn.,  the  double  pored  tapeworm. 

Biting  lice  or  larval  fleas  become  infected  with  the  larval  stage 
of  this  parasite  by  eating  particles  of  the  dogs  feces  containing  the 
"eggs"  of  this  worm.  The  young  form  develops  in  the  louse  or 
flea  and  when  these  are  eaten  by  the  dog  the  larval  tapeworm  avoids 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  67 

digestion,  attaches  itself  to  the  lining  of  the  intestine  and  becomes  a 
mature  tapeworm.  The  most  efficient  treatment  is  arecoline  hydro- 
bromide  in  y8-  to  i/4-grain  doses  placed  on  the  tongue  of  the  animal. 
With  valuable  dogs  or  toy  dogs  this  treatment  should  be  administered 
by  a  veterinarian  who  would  be  able  to  recognize  symptoms  of  poison- 
ing and  apply  the  necessary  antidotes.  No  preparation  is  necessary 
and  the  tapeworms  are  generally  eliminated  in  from  ten  to  fifteen 
minutes. 

SWINE 

Lice,  Haematopinas  suis  Linn. — The  control  of  the  sucking  lice  of 
hogs  is  extremely  important.  The  irritation  together  with  the  loss  of 
blood  occasioned  by  their  attacks  is  the  cause  of  considerable  losses 
when  taken  in  the  aggregate.  Crude  oil  is  the  best  remedy.  This 
may  be  applied  by  soaking  it  on  burlap-wound  posts  in  the  corrals 
against  which  the  hogs  will  rub,  or  by  applying  it  to  the  surface 
of  their  wallows  if  the  latter  are  located  in  the  shade. 

Scabies  or  Mange,  Common,  see  "  Sheep. " —  Demodectic,  see 
"Dogs." 

The  control  of  demodectic  mange  on  hogs  is  seldom  of  economic 
importance,  as  the  disease  affects  only  the  skin  and  is  seldom  serious 
during  the  relatively  short  life  of  the  breeding  stock.  The  same 
measures  may  be  taken  as  for  dogs.  The  snout  and  face  about  the 
eyes  are  the  parts  generally  affected. 

Roundworms,  Ascaris  lumbricoides  Linn. — For  life  history  see 
"Dogs." 

Treatment — Starve  the  infested  animals  for  twenty-four  hours. 
Administer  individually  4  c.c.  of  oil  of  chenopodium  and  1  ounce  of 
castor  oil  to  each  hog  of  less  than  100  pounds  and  twice  the  dose 
for  those  over  this  weight. 

GROUND  SQUIRRELS 

The  five  most  effective  methods  of  destroying  ground  squirrels  are  : 
(1)  poisoning  with  strychnine;  (2)  fumigation  with  carbon  bisul- 
phid  (3)  trapping;  (4)  shooting;  (5)  encouragement  of  the  natural 
enemies  of  the  ground  squirrel.     (See  Circ.  181.) 

1.  Carbon  bisulphid  is  most  effective  when  the  soil  is  damp. 
When  the  ground  is  dry  the  gas  escapes  through  the  cracks  in  the 
ground. 


68  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

2.  Strychnine-coated  barley  is  best  used  during  the  dry  season 
because  at  this  time  the  squirrels  gather  and  store  grain  and  hence 
are  easily  poisoned  through  their  cheek  pouches  when  in  the  act  of 
carrying  the  poisoned  grain.  Rain  and  heavy  fogs  tend  to  wash  the 
strychnine  off  the  poisoned  grain. 

3.  Trapping  and  shooting  are  effective  at  any  time,  but  are  from 
six  to  twelve  times  more  so  before  the  young  are  out,  before  April  1, 
than  later  in  the  season. 

4.  Powdered  strychnine  (sulfate)  in  fresh  vegetables  and  fruit 
is  especially  effective  in  the  dry  season  when  green  food  is  scarce. 
(Formula  33.) 

5.  Red-tailed  hawks,  Golden  eagles,  badgers,  weasels,  and  other 
natural  enemies  of  the  ground  squirrel  will  prove  valuable  allies  in 
the  war  on  ground  squirrels  if  they  are  only  allowed  to  live.  It  costs 
little  to  let  them  alone  to  go  about  their  business  in  the  natural  way. 

GOPHERS 

The  five  most  effective  methods  of  destroying  gophers  are:  (1) 
poisoning  with  strychnine ;  (2)  trapping;  (3)  flooding;  (4)  fumigation 
with  carbon  bisulphid;  (5)  for  permanent  relief,  the  encouragement 
and  protection  of  the  gopher 's  natural  enemies,  especially  the  barn  owl 
and  the  gopher  snake. 

The  solution  of  the  gopher  problem  lies  in  a  combination  of  two 
or  more  of  the  above  methods,  rather  than  in  any  one  of  them. 
Where  a  large  acreage  is  to  be  treated,  poisoning  with  strychnine 
(Formula  34)  will  be  found  most  effective  in  reducing  the  pest.  Traps 
are  safe,  can  be  used  at  any  time,  and  are  effective  in  the  hands  of  a 
man  who  is  not  afraid  to  dig  and  who  uses  care  in  setting  and  placing 
them.  Trapping  is  especially  adapted  to  pastures,  where  there  might 
be  danger  of  poisoning  stock,  and  to  gardens,  orchards,  and  the  banks 
of  irrigation  ditches.  Carbon  bisulphid  should  be  used  only  when 
the  ground  is  wet.  Both  traps  and  carbon  bisulphid  are  good 
"follow-up"  methods  in  getting  the  gophers  which  refuse  to  take 
poisoned  bait.  Land  that  can  be  successfully  flooded,  so  as  to  drown 
out  the  gophers,  has  usually  been  graded  for  irrigation  crops  such  as 
alfalfa.  Flooding  (irrigation)  is  therefore  automatic,  and  it  is  com- 
paratively easy  to  hunt  and  kill  gophers  which  are  being  flooded  out. 
A  man  that  kills  all  gopher  snakes  and  barn  owls  on  his  place  will 
have  to  fight  gophers,  and  deservedly  so.     (See  Bull.  No.  340.) 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  69 


RABBITS 

If  very  abundant,  must  be  fenced  out  of  young  orchards  and  gar- 
dens to  avoid  serious  damage.  Shooting  and  poisoning  are  the  prin- 
cipal means  of  destruction.  An  application  of  whitewash  containing 
bitter  aloes  to  the  trunks  of  young  trees  is  sometimes  recommended, 
but  this  has  not  shown  much  value  in  actual  practice. 

Soaked,  chopped  alfalfa  sprinkled  with  strychnine,  Paris  green  or 
white  arsenic  is  very  effective  in  destroying  cotton-tails. 


RATS 

These  pests  should  be  handled  by  trapping  if  possible.  Spring 
traps  should  be  used,  baited  with  fried  bacon  and  the  entire  trap 
flamed  with  a  burning  newspaper  before  setting.  When  traps  fail,  a 
poison  bait  made  by  mixing  barium  carbonate  with  bananas,  ham- 
burger steak,  or  moistened  bran  mash  in  the  proportion  of  1  part  of 
poison  to  4  parts  of  the  carrier  may  be  used. 


VENOMOUS  INSECTS,   SPIDERS,   ETC. 

Among  the  few  venomous  insects,  spiders,  etc.,  the  most  noteworthy 
are  the  so-called  kissing  bugs  (cone  noses),  hour  glass  or  shoe  button 
spider,  the  pajaroello  tick  and  the  scorpion.  Two  species  of  kissing 
bugs  (Triatoma  protracta  Uhler,  a  black  species,  also  known  as  the 
China  bed  bug  or  cross  bug,  and  Rasahus  thoracicus  Stal,  the  two- 
spotted  corsair,  a  reddish-brown  species  with  a  large  brick  red  spot 
on  each  wing  cover)  inflict  particularly  painful  bites  which  in  turn 
may  result  in  more  or  less  severe  symptoms  such  as  vomiting  and  rash. 

These  insects  usually  bite  at  night,  but  may  also  do  so  when 
disturbed  during  the  day.  Bathing  the  wound  immediately  with  a 
1  to  1000  solution  of  mercuric  chloride  (poison)  or  strong  ammonia 
will  afford  some  relief.  The  same  treatment  may  be  applied  for  the 
sting  of  scorpions. 

The  bite  of  the  shoe  button  spider  (Latrodectes  mactans  Fabr.) 
and  that  of  the  pajaroello  tick  (Omithodorus  coreaceus  Koch)  may 
prove  serious,  and  a  physician  should  be  consulted.  The  immediate 
application  of  potassium  permanganate  is  recommended. 


70  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

FORMULAS  AND  DESCRIPTIONS  OF  MATERIAL* 

ARSENICALS 

Acid  Lead  Arsenate  (Lead  Hydrogen  Arsenate,  Di-lead  Arsenate, 
Often  Labeled  "Standard"  or  Lead  Arsenate). — The  acid  type  of  lead 
arsenate  contains  more  poison  per  pound  than  the  basic  type,  is  a 
stronger  poison  and  acts  more  quickly.  It  is,  however,  somewhat  sus- 
ceptible to  the  action  of  other  chemicals,  particularly  those  of  an  alka- 
line nature  (such  as  soaps,  lime-sulfur  solution,  etc.),  and  is  more  or 
less  dissolved  by  them  when  used  as  a  combination  spray.  In  moist 
climates  along  the  coast,  or  in  continuous  damp,  cloudy  weather  else- 
where, whether  used  alone  or  in  combination  with  other  sprays,  some 
of  the  arsenic  is  apt  to  be  dissolved  and  to  cause  serious  foliage  injury. 
It  is  not  considered  a  safe  arsenical  for  use  on  stone  fruits,  beans,  or 
other  susceptible  plants. 

Basic  Lead  Arsenate  (Usually  Labeled  "Tri-plumbic"  or  " Neu- 
tral").— The  basic  type  of  lead  arsenate  is  a  weaker  poison  and  acts 
more  slowly.  It  is  not  decomposed,  however,  by  chemicals  of  an  alka- 
line nature,  such  as  are  usually  applied  with  it  as  a  combination  spray, 
nor  by  the  damp  weather  of  the  coast  regions.  It  is  considered  the 
only  safe  arsenical  to  use  on  stona  fruits,  beans,  or  other  susceptible 
plants. 

The  lead  arsenates  are  usually  sold  as  a  paste  containing  about 
50  per  cent  of  water,  or  as  a  dry  powder.  The  paste  should  be  thinned 
somewhat  with  water  and  worked  into  a  smooth  cream  before  adding  to 
the  spray  tank.  The  powder  may  be  added  directly  to  the  tank  and 
mixed  by  means  of  the  agitator. 

For  codling  moth  and  most  defoliating  insects  use : 

Formula  1 

Dry  acid  lead  arsenate  (paste,  4  to  8  pounds) 2  to  4  pounds 

Water 100  gallons 

Or  Formula  2 

Dry  basic  lead  arsenate  (paste,  5  to  10  pounds) 2%  to  5  pounds 

Water 100  gallons 

Dry  or  powdered  lead  arsenate  contains  twice  as  much  arsenic  as 
the  paste;  therefore  use  only  one-half  as  much  of  it. 

*  Mr.  Geo.  P.  Gray  furnished  much  of  the  information  relative  to  the 
chemical  compositions  and  reactions  of  these  insecticides. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  71 

Zinc  Arsenite  is  a  stronger  and  more  active  poison  than  either  type 
of  lead  arsenate,  and  is  useful  in  controlling  the  various  caterpillars 
which  are  troublesome  on  pears  and  apples  in  the  early  spring,  but  is 
very  apt  to  cause  injury  if  the  application  is  made  after  the  time  of 
full  bloom. 

Formula  3 

Zinc  arsenite  powder  3  pounds 

Water  100  gallons 

White  arsenic  (Arsenic  trioxide)  is  only  sparingly  soluble  in 
water,  although  sufficiently  so  to  prohibit  its  use  on  plants  as  an 
insecticide.  Its  use  as  a  stomach  poison  is  therefore  limited  to  the 
preparation  of  poison  baits  for  the  control  of  grasshoppers,  army- 
worms,  cutworms,  etc.,  and  to  some  other  cases  where  the  insecticide 
is  not  to  be  applied  to  growing  plants. 

Formula  3a 

Government  Arsenical  Dip. 

Caustic  soda  4  pounds 

White  arsenic  8  pounds 

Sal  soda  crystals 8  pounds 

Pine  tar    1  gallon 

Water  to  make    500  gallons 


Dissolve  the  caustic  soda  in  an  iron  vessel  (zinc,  tin  or  solder 
will  be  corroded)  using  1  gallon  of  water.  Then  add  the  arsenic 
slowly,  with  constant  stirring.  The  temperature  of  the  solution  while 
mixing  should  be  just  below  boiling.  Add  the  sal  soda  after  the 
arsenic  is  dissolved,  stir,  then  make  up  to  5  gallons. 

Emulsify  the  pine  tar  by  dissolving  %  of  a  pound  of  caustic  soda 
or  concentrated  lye  in  1  quart  of  water  and  adding  to  this  1  gallon 
of  pine  tar.  Stir  until  a  clear  molasses-like  liquid  results.  If  a 
drop  of  this  does  not  mix  perfectly  with  water,  stir  in  caustic  soda 
until  a  perfect  mixture  of  tar  and  water  results. 

To  prepare  the  dip,  dilute  the  emulsified  tar  with  two  or  three 
times  its  volume  of  water  and  pour  this  into  the  dipping  tank,  after 
the  latter  is  three-fourths  full.  Add  the  arsenical  solution  in  the 
same  way  and  make  up  to  the  desired  amount. 

This  solution  is  very  poisonous  and  should  be  handled  and  disposed 
of  with  great  care. 


72  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Poison  Bran  Mash. 

Formula  4 

Bran   25  pounds 

White  arsenic 1  pound 

Molasses  (cheap  blackstrap  preferred)   2  quarts 

Mix  the  arsenic  and  the  bran  dry  and  add  the  molasses  which  has 
been  diluted  with  water.  Add  enough  water  and  mix  thoroughly  to 
make  a  dry  mash  which  will  broadcast  easily. 

Citrus  Bran  Mash. 

Formula  5 

White  arsenic   1  pound 

Molasses  (cheap  blackstrap  preferred)  2  quarts 

Lemons  (or  oranges)  6  fruits 

Water  (about)  4  gallons 

Bran   25  pounds 

Mix  the  above  materials  as  follows:  Stir  thoroughly  the  white 
arsenic,  molasses,  and  water  first.  Grind  the  lemons,  including  the 
rinds,  in  a  meat  grinder,  or  chop  fine,  and  add  to  this  liquid.  Then 
slowly  pour  this  over  the  bran  and  stir  thoroughly  until  an  even  mix- 
ture is  secured. 

The  amount  of  water  to  use  in  the  preparation  of  these  baits  will 
vary  according  to  the  coarseness  of  the  bran  or  substitutes.  A  barely 
moist  mash  is  preferable  to  a  wet  one  because  it  does  not  harden  under 
the  heat  of  the  sun  and  remains  palatable,  while  wet  mash  becomes 
baked  and  unattractive. 

Substitutes  in  Poison  Baits. — Paris  green  may  be  substituted  for 
white  arsenic  in  Formulas  4  and  5.  Alfalfa  meal,  shorts,  or  rice  meal 
have  been  successfully  used  as  a  substitute  for  bran  in  the  preparation 
of  the  above  formulas. 

Sodium  Arsenite. — This  arsenical  is  readily  soluble  in  water  and 
is  one  of  the  most  violent  of  the  plant  poisons.  It  probably  acts  more 
quickly  than  any  of  the  better-known  arsenical  poisons,  and  is  com- 
monly used  in  the  preparation  of  weed  killers,  poison  fly-papers,  cattle 
dips  for  the  control  of  ticks,  ant  syrups,  and  to  some  extent  in  the 
preparation  of  poison  baits. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  73 

Sodium  arsenite  may  be  purchased  ready  made  as  a  white  powder, 
but  it  is  not  always  readily  obtained  at  pharmacies,  nor  can  it  always 
be  depended  upon  to  contain  a  uniform  amount  of  arsenic.  This 
chemical  may  be  easily  prepared  from  white  arsenic  by  combining  the 
latter  in  the  presence  of  water  with  sal  soda,  soda  ash,  caustic  soda, 
or  a  good  grade  of  concentrated  lye  in  the  following  proportions : 

Sal  soda  or  washing  soda,  2  parts  to  1  part  of  white  arsenic. 
Soda  ash,  1  part  to  1  part  of  white  arsenic. 
Caustic  soda,  1  part  to  2  parts  of  white  arsenic. 
Concentrated  lye,  1  part  to  2  parts  of  white  arsenic. 

If  sal  soda  or  soda  ash  is  used  it  is  necessary  to  boil  the  mixture 
fifteen  or  twenty  minutes  before  the  arsenic  is  dissolved.  If  caustic 
soda  or  concentrated  lye  is  used,  little  or  no  heat  is  necessary.  In 
either  case,  a  corrosive  chemical  known  as  sodium  arsenite  is  formed. 

A  soluble  arsenical  can  be  made  by  using  1  part  of  caustic  soda 
to  4  parts  of  white  arsenic  (arsenic  AS2  03)  trioxide,  such  a  solution, 
however,  has  a  tendency  to  form  crystals  on  standing. 

Sodium  Arsenite. 

Formula  6 

Sal  soda 2  ounces  (or  2  pounds) 

White  arsenic 1  ounce  (or  1  pound) 

Water  (about)  y2  pint  (or  1  gallon) 

Put  all  the  ingredients  together  in  an  iron  or  graniteware  kettle 
(do  not  use  aluminum)  of  sufficient  size  to  allow  for  considerable 
frothing,  and  boil  fifteen  or  twenty  minutes,  or  until  the  solution  is 
clear. 

Ant  Syrups. 

Formula  7 

Strong  for  Weak  for  Argentine  ants 

native  ants        Large  quantity  Small  quantity 

White  arsenic  2  oz.  1  oz.  1  scruple 

Concentrated  lye  1  oz.  1  oz.  y2  teaspoonful 

Sugar  1  lb.  20  lbs.  1  lb. 

Water 1  pt.  3  gals.  1  pt. 

The  U.  S.  Bureau  of  Entomology  recommends  a  later  formula  for 
the  preparation  of  Argentine  ant  syrup  which  is  said  to  be  superior 
to  any  other  formula  tested  by  them,  "on  account  of  its  stability  at 
high  temperatures,  freedom  from  crystalization,  and  continued  attrac- 
tiveness. ' ' 


74  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Government  Argentine  Ant  Syrup. 

Formula  8 

Granulated  sugar 12  pounds 

Water 11  pints 

Tartaric  acid  (crystalized)  7  grams 

Benzoate  of  soda 9  grams 

Boil  slowly  for  30  minutes.     Allow  to  cool. 

Dissolve  sodium  arsenite  (C.  P.)  %  ounce 

In  hot  water y2  pint 

Cool.     Add  poison  solution  to  syrup  and  stir  well. 

Add  to  the  poisoned  syrup : 
Honey,  strained 2  pounds 

Mix  thoroughly. 


COPPER  COMPOUNDS 

Bordeaux  Mixture  (Average  Strength). 

Formula  9 

Bluestone   16  pounds 

Quicklime 20  pounds 

Water  200  gallons 

Dissolve  the  bluestone  and  slake  the  lime  in  separate  vats,  the  blue- 
stone  to  be  kept  from  contact  with  all  metals  except  copper.  Thor- 
oughly mix  the  dissolved  bluestone  with  one-half  the  water  and  the 
slaked  lime  with  the  other  half.  Run  the  two  mixtures  together  in  a 
single  stream  into  the  spray  tank  through  a  fine  screen.  For  conven- 
ience, the  mixing  vats  may  be  placed  on  an  elevated  platform,  and  the 
two  parts  mixed  as  they  are  flowing  into  the  spray  tank.  The  milk  of 
lime  should  be  continuously  stirred  during  the  mixing. 

A  somewhat  less  satisfactory  Bordeaux  mixture  may  be  made  as 
follows :  Slake  the  lime  and  dissolve  the  bluestone  in  separate  barrels 
as  above.  Fill  the  spray  tank  half  full  of  water;  add  the  dissolved 
bluestone ;  strain  in  the  slaked  lime  while  the  agitator  is  running ;  add 
remainder  of  water,  and  mix  thoroughly. 


Bordeaux  Paste. 

Formula  10 

A.  Bluestone  12  pounds 

Water  8  gallons 

B.  Quicklime  24  pounds 

Water 8  gallons 

Dissolve  the  bluestone  and  slake  the  lime  separately  in  the  amounts 
of  water  specified.  Then  mix  together  equal  quantities  of  each  ingre- 
dient, making  up  only  enough  for  each  day's  use. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  75 

Commercial  Bordeaux  Mixture. — Several  preparations  of  this  sort 
are  on  the  market  in  the  form  of  a  paste  or  dry  powder  to  be  diluted 
with  water.  Objection  is  sometimes  made  to  these  preparations  that 
they  will  not  remain  in  suspension  in  water  as  well  as  the  home-made 
Bordeaux  mixture,  but  some  of  them  are  probably  as  good  or  better 
than  the  average  mixture  prepared  on  the  ranch.  The  commercial 
preparations  are  more  expensive,  but  also  more  convenient  for  use, 
and  are  of  especial  value  to  the  small  grower. 

Resin-Bordeaux  Mixture. 

Formula  10a 

Bluestone   _ 20  pounds 

Lime   26  pounds 

Resin  10  pounds 

Soap   (soft)   16  pounds 

Water  200  gallons 

Melt  the  resin  in  an  iron  pot ;  then  add  the  soft  soap,  heat  and  stir 
until  well  mixed  and  quite  soft.  Add  hot  water  and  boil  and  stir  for 
some  time  until  thoroughly  dissolved.  Add  this  to  the  Bordeaux 
which  has  been  made  in  the  usual  way.  (From  Univ.  Calif.  Exp. 
Sta.  Bull.  165,  p.  77.)  This  is  for  use  on  plants  with  very  smooth 
waxy  surfaces  on  which  fungicides  do  not  spread  and  adhere  well. 

Bluestone  (Copper  Sulfate). — A  soluble  compound  of  copper,  the 
raw  material  for  the  preparation  of  most  other  compounds  of  copper. 
This  cannot  be  used  on  foliage. 

For  dipping  grain  use : 

Formula  11 

Bluestone   1  pound 

Water  5  gallons 

Dip  for  3  minutes. 

Followed  by: 

Quicklime 1  pound 

Slaked  in  water 10  gallons 

For  lemon  wash  water  use: 

Formula  12 

Bluestone   1%  pounds 

Water  1000  gallons 

Copper  Carbonate. — For  dust  treatment  of  grain,  use  Formula 
11a.  For  dusting  wheat  for  bunt,  use  2  ounces  of  copper  carbonate 
dust  to  a  bushel.     The  dust  should  be  intimately  mixed  to  thoroughly 


76  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

cover  each  seed.  The  copper  corbonate  dust  should  contain  50  per 
cent  of  copper  in  the  form  of  carbonate  and  hydrate  of  copper,  and 
should  be  sufficiently  fine  to  weigh  approximately  32  pounds  to  a 
cubic  foot.  The  dusted  seed  may  be  stored  without  injury  from  the 
dust. 

Ammoniacal  solution  of  copper  carbonate. — This  solution  contains 
no  sediment  and  on  drying  leaves  no  unsightly  marks.  It  may  there- 
fore be  used  when  the  spotting  that  the  Bordeaux  mixture  causes 
precludes  the  use  of  that  fungicide.  The  mixture  consists  of  a  solution 
made  by  dissolving  copper  carbonate  in  ammonia-water  in  the  follow- 
ing proportions: 

Copper  carbonate  6  oz. 

Ammonia,  about  3  pints 

Water  50  gals. 

Weigh  out  the  proper  amount  of  copper  carbonate.  Set  a  very 
small  portion  of  this  aside  and  dissolve  the  remainder  of  it  in  diluted 
ammonia  (dilute  ammonia  with  water  to  about  5  times  its  volume), 
using  only  enough  ammonia  to  dissolve  it.  Then  add  the  portion  of 
copper  carbonate  which  was  reserved.  This  will  insure  the  use  of  no 
more  ammonia  than  is  necessary.  It  is  better  to  have  a  little  too 
much  of  the  carbonate  in  the  solution  than  to  have  too  much  ammonia. 
The  strong  solution  made  in  this  way  may  be  diluted  with  the  proper 
amount  of  water.  The  copper  carbonate  may  be  purchased  directly 
from  the  drug  store,  or  it  may  be  prepared  at  home. 

SULFUR  AND  SULFUR  COMPOUNDS 

Dry  Sulfur. — For  dusting  upon  plants  for  the  control  of  surface 
mildew,  red  spider,  or  other  parasites,  the  fineness  of  the  sulfur  is  an 
all-important  consideration.  Flowers  of  sulfur,  the  finest  and  fluffiest 
grade  of  sublimed  sulfur,  has  been  heretofore  recommended  for  appli- 
cation as  a  dust,  but  at  present  there  are  upon  the  market  several 
brands  of  extremely  finely  ground  sulfurs,  which  are  as  fine  as  some 
of  the  best  grades  of  sublimed  sulfur  and  no  more  expensive.  Some 
of  these  sulfurs,  which  have  been  specially  prepared  for  dusting,  are 
ground  to  pass  a  200-mesh  bolting  cloth.  These  are  apt  to  cake  and 
to  clog  the  dusting  apparatus.  If  9  parts  of  sulfur  are  thoroughly 
mixed  with  1  part  of  hydrated  lime,  kaolin,  or  other  inert  powder, 
these  difficulties  may  be  avoided. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  77 

Sulfur  Pastes  or  Wettable  Sulfurs. — For  various  reasons  it  is  often 
desirable  to  mix  sulfur  and  water  and  apply  it  to  plants  as  a  spray. 
Sulfur,  however,  is  not  easily  wetted  with  water  and  it  is  a  difficult 
matter  to  make  a  uniform  mixture  of  the  two.  It  has  been  found  that 
a  number  of  substances — soap,  calcium  casemate,  oleic  acid,  glue, 
diatomaceous  earth,  flour,  dextrin,  etc. — when  mixed  with  water  and 
sulfur  have  the  property  of  counteracting  the  mutual  repulsion  of 
sulfur  and  water  without  otherwise  altering  the  nature  of  the  sulfur. 
Certain  of  these  substances  have  been  used  in  the  preparation  of 
commercial  sulfur  pastes  or  wettable  sulfurs.  These  commercial 
pastes,  as  now  manufactured,  contain  from  45  to  50  or  more  per 
cent  of  sulfur  in  a  very  finely  divided  condition,  the  remainder  being 
water  and  one  of  the  substances  mentioned  above.  The  effect  of  these 
pastes  is  that  of  dry  sulfur.     The  usual  strength  to  use  is : 

Formula  13 

Commercial  sulfur  paste  8  to  21  pounds 

Water   100  gallons 

Home-Made  Wettable  Sulfur. — A  satisfactory  wettable  sulfur  can 
be  easily  made  at  home  by  the  use  of  glue  water  as  follows : 

Formula  14 

Powdered  glue  %  ounce 

Hot  water  iy2  gallons 

Sulfur  (flowers  or  powdered)  5  pounds 

Water  to  make 100  gallons 

Dissolve  the  glue  in  hot  water  or  soak  over  night  in  iy2  gallons 
of  cold  water.  Add  the  glue  water  to  the  sulfur  a  little  at  a  time 
and  work  up  into  a  smooth  paste  as  free  from  lumps  as  possible. 
Rubbing  is  better  than  stirring.  Wash  this  paste  into  the  spray  tank 
through  a  fine  screen,  using  the  remainder  of  the  glue  water  to  wash 
it  through  and  a  stiff  brush  to  break  up  the  remainder  of  the  lumps. 
Then  add  plain  water  to  make  100  gallons. 

Another  formula  more  expensive  than  the  above  is : 

Formula  15 
Make  a  paste  of: 

Flour 4  pounds 

Water  4  gallons 

Mix  this  with: 

Sulfur  (sublimed  or  powdered)  5  pounds 

Then  add : 

Water  to  make 100  gallons 


78  university  of  california — experiment  station 

Formula  15a 

Self-Boiled  Lime-Sulfur  Wash. — A  preparation  of  sulfur  largely 
used  in  the  eastern  states  for  a  summer  spray  on  peach  and  other 
tender  foliage  and  comparable  in  use  with  the  wettable  sulphur 
preparations. 

Quicklime  32  pounds 

Sulfur  32  pounds 

Water  to  make 200  gallons 

Put  the  quicklime  in  a  suitable  container  and  add  water  to  start 
slaking,  about  12  gallons  (hot  water  for  sluggish  lime  and  cold  for 
active.)  Work  the  sulfur  through  a  sieve  and  add  to  the  lime  with 
stirring  to  prevent  caking.  Add  enough  water  to  make  a  paste. 
When  the  violent  boiling  ceases,  add  cold  water  to  make  up  to  the 
final  amount.  If  allowed  to  stand  hot,  the  mixture  becomes  caustic. 
The  wash  must  be  strained  and  applied  with  a  pump  having  a  good 
agitator. 

The  usual  grades  of  sublimed  or  powdered  sulfur  may  be  wetted 
in  the  manner  described  in  Formulas  14  and  15,  but  for  the  best 
results  the  finest  grade  of  sulfur  obtainable  should  be  used.  The 
sulfurs  especially  prepared  for  dusting  are  recommended  for  this 
purpose. 

Lime-Sulfur  Solution.-^This  is  the  most  active  form  in  which 
sulfur  compounds  are  commonly  used  in  the  control  of  insects  or 
fungi.  Its  causticity  prohibits  its  use  on  any  foliage  except  that  of  the 
more  hardy  plants,  and  then  in  a  very  dilute  form.  Its  principal 
use  is  as  a  dormant  spray  for  the  control  of  certain  fungus  diseases, 
scale  insects,  red  spider,  and  a  variety  of  other  pests  of  deciduous 
trees. 

Commercial  Lime-Sulfur  Solution. — The  horticulturists  of  the 
state  are  being  supplied  with  concentrated  commercial  lime-sulfur 
solution  of  good  quality  and  at  reasonable  prices.  The  great  bulk 
of  this  important  pest  remedy  used  in  the  state  is  therefore  of  com- 
mercial manufacture,  testing  between  32°  and  34°  Baume.  It  is  only 
necessary  to  dilute  this  with  water  before  spraying. 

Home-Made  Lime-Sulfur  Solution. 

Formula  17 

Stone  lime 50  pounds 

Sulfur  (sublimed  or  powdered)  100  pounds 

Water  to  make 50  gallons 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  79 

Heat  about  one-third  of  the  total  volume  of  water  required.  When 
the  water  is  hot  add  all  of  the  lime,  and  then  immediately  all  the 
sulfur,  which  should  previously  have  been  made  into  a  thick  paste  with 
water.  After  the  lime  is  slaked  another  third  of  the  water  should 
be  added,  preferably  hot,  and  the  cooking  should  be  continued  until 
a  clear  orange-colored  solution  is  obtained  (usually  45  to  60  minutes), 
when  the  remainder  of  the  water  should  be  added,  either  hot  or  cold, 
as  is  most  convenient.  The  boiling  due  to  the  slaking  of  the  lime 
thoroughly  mixes  the  ingredients  at  the  start,  but  subsequent  stirring 
is  necessary  if  the  wash  is  cooked  by  direct  heat  in  a  kettle.  After 
the  wash  has  been  prepared  it  must  be  allowed  to  settle  and  then 
strained  through  a  fine  sieve  as  it  is  being  run  into  the  spray  tank. 
The  resultant  product  is  a  concentrated  solution  of  lime-sulfur,  which 
should  be  diluted  about  six  times  with  water  for  a  winter  spray. 

Dry  Lime-Sulfur. 

Lime-sulfur  is  now  obtainable  in  the  form  of  a  dry  powder  which 
is  used  by  dissolving  in  water.  40  pounds  to  200  gallons  of  spray 
is  usually  recommended  for  application  on  dormant  trees.  A  strength 
of  about  10  pounds  to  200  gallons  is  generally  recommended  for  use 
on  foliage  as  in  treating  apple  scab,  red  spiders,  etc. 

The  recommendations  for  the  dry  lime-sulfur  sprays  call  for 
the  use  of  a  smaller  amount  of  total  sulfur  in  general  than  is  used 
with  the  liquid  lime-sulfur  solution,  but  the  comparative  efficiency 
of  the  preparations  seems  not  to  be  fully  determined. 

Formula  17a 
Lime-Sulfur  Dip. 

Lime  (unslaked)  8  pounds 

(or  11  pounds  of  commercial  hydrated  lime) 

Flowers  of  sulfur  24  pounds 

Water  100  gallons 

Slake  the  lime,  sift  in  the  sulfur  and  make  a  thin  paste ;  add 
water  to  make  30  gallons,  and  boil  for  one  hour,  stirring  during  the 
process.  Add  water  while  cooking  to  maintain  the  original  amount 
of  30  gallons.  Strain  or  siphon  off  the  liquid  and  make  up  to  100 
gallons.  An  excess  of  lime  or  sediment  in  the  dip  will  injure  the 
sheep  and  wool. 

The  standard  lime-sulfur  dip  as  made  above  may  be  combined 
with  one-half  standard  arsenical  dip  (see  Formula  3a)  for  sheep 
1  Hicks." 

Alkali  Sulfides. — Sulfides  of  soda  ("soluble  sulfur")  are  some- 
times used  in  place  of  lime-sulfur  solution  and  have  some  advantages 
over  the  liquid  preparations. 


80  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


PDB  or  PARA-DICHLOROBENZENE,  A  NEW  SOIL  FUMIGANT 

The  use  of  para-dichlorobenzene  as  a  soil  fumigant  to  control 
soil  infesting  insects  has  created  a  large  interest  in  California.  The 
experiments  conducted  during  the  past  two  years,  while  not  exten- 
sive, will  be  of  interest  in  outlining  a  larger  practice  for  next  season. 

The  material  in  question  is  a  white  crystalline  substance  which 
is  insoluble  in  water  and  evaporates  slowly  at  a  temperature  of  55° 
to  75°  F.  and  more  rapidly  at  higher  temperatures.  The  vapor  is 
more  than  five  times  heavier  than  air  and  more  than  twice  as  heavy 
as  carbon  bisulfide  vapor.  It  possesses  a  weak  ether-like  odor  which 
is  practically  nonpoisonous  and  noncombustible. 

Common  name  of  material. — Para-dichlorobenzene  has  such  a  long 
name  that  it  seems  advisable  to  abbreviate  it  by  using  P.  D.  B.  for 
short.  Various  trade  names  such  as  "Paracide,"  " Crystal  Glass," 
etc.,  are  already  appearing,  and  many  others  will  soon  follow. 

Conditions  of  application. — In  applying  the  material  two  things 
are  important ;  soil  moisture  and  temperature.  Because  gases  do  not 
readily  circulate  in  a  thoroughly  wet  soil  it  is  useless  to  apply  para- 
dichlorobenzene  unless  the  soil  is  not  more  than  ordinarily  moist, 
as  is  usually  the  case  in  California  during  the  summer  and  fall  except 
just  after  irrigations.  In  such  cases  a  week  or  two  following  the 
application  of  water  would  be  preferable.  The  soil  temperature 
should  range  from  75°  to  85°  F.  for  the  best  results,  for  under  such 
conditions  the  para-dichlorobenzene  volatilizes  more  rapidly  and  the 
insects  are  more  active,  requiring  a  greater  air  supply,  and  are  con- 
sequently more  readily  killed  by  the  vapor. 

Time  of  application. — In  California  the  period  from  the  first  of 
May  until  November  may  be  roughly  designated  as  the  proper  time 
to  make  the  applications,  provided  the  soil  temperature  is  over  55°  F. 
and  the  soil  moisture  is  not  excessive. 

Methods  of  application. — From  %  to  1  ounce  of  para-dichloro- 
benzene is  sufficient  to  treat  an  average  size  tree.  First,  level  the 
surface  of  the  soil  around  the  base  of  the  tree;  then  sprinkle  the 
material  around  the  tree  in  a  contiuous  band  or  circle  two  inches  wide 
with  the  inner  margin  two  to  four  inches  from  the  bark  of  the  tree. 
Cover  the  material  with  soil  around  the  base  of  the  tree  to  a  depth 
of  from  two  to  four  inches  and  pack  well  with  several  strokes  of 
the  shovel. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  81 

Kinds  of  trees  to  treat. — Under  eastern  conditions,  where  the  use 
of  this  insecticide  has  been  quite  extensive,  it  has  been  applied  chiefly 
to  peach  trees  on  peach  root-stocks.  The  eastern  investigators  caution 
against  using  it  on  trees  under  six  years  of  age,  although  younger  trees 
are  reported  to  have  been  treated  with  no  injurious  results  in  many 
instances. 

In  California  apricot  trees  on  Myrobalan  rootstock  and  infested 
with  the  peach  tree  borer  have  been  treated  with  .good  results  in 
killing  the  borers  without  injury  to  the  trees. 

Even  nursery  stock  on  Myrobalan  and  peach  roots  treated  in  the 
early  summer  showed  no  ill  effects,  but  such  work  should  receive 
more  attention  before  general  recommendations  can  be  made. 

California  conditions  are  so  different  from  those  in  the  southern 
and  eastern  states  that  it  is  to  be  expected  that  we  shall  encounter 
many  unusual  problems  in  the  handling  of  the  material  and  that  its 
uses  may  be  very  greatly  enlarged.  The  Division  of  Entomology 
and  Parasitology  is  contemplating  a  large  series  of  orchard  demon- 
strations and  experiments  during  the  coming  year  in  order  to  have 
as  much  local  information  as  it  is  possible  to  accumulate  in  that 
time. 

Not  for  flat-headed  borers. — Para-dichlorobenzene  is  being  recom- 
mended by  some  insecticide  dealers  for  all  woodboring  insects,  par- 
ticularly for  the  flat-headed  apple  tree  borer.  This  insect  and  the 
other  wood  borers  which  work  above  ground  cannot  be  satisfactorily 
reached  by  the  fumes  of  the  fumigant  and  cannot  be  controlled  by  it! 

CRUDE  PETROLEUM 

The  use  of  crude  petroleum  is  almost  entirely  limited  to  the  winter 
spraying  of  deciduous  trees  when  the  buds  are  entirely  dormant.  It 
is  generally  applied  from  November  to  February.  The  crude  oil  emul- 
sion is  especially  recommended  for  black  scale  (Saissetia  oleae),  Euro- 
pean fruit  Lecanium  (Lecanium  corni),  European  or  Italian  pear  scale 
(Epididiaspis  piricola),  cherry  scale  (Lecanium  cerasorum) ,  and  other 
scales  infesting  deciduous  fruit  trees.  It  is  practically  the  only  spray 
treatment  which  has  been  effective  against  European  or  Italian 
pear  scale,  and  will  destroy  the  winter  eggs  of  many  of  the  aphids,  of 
the  red  spider,  and  of  some  of  the  defoliating  caterpillars. 

When  crude  oil  is  thoroughly  applied  it  sometimes  penetrates  the 
fruit  buds  to  a  considerable  extent,  and  may  injure  and  even  kill  some 
of  them.  The  great  majority  of  the  buds  are  not  injured,  however, 
but  appear  to  be  stimulated  to  a  more  vigorous  growth,  and  to  the 


82  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

production  of  foliage  resistant  to  disease.  It  is  good  practice,  especi- 
ally in  dry  seasons,  not  to  apply  crude  oil  emulsion  until  there  is 
indication  of  swelling  of  the  buds. 

A  natural  crude  petroleum,  testing  about  23°  Baume,  is  preferred, 
as  it  contains  some  of  the  lighter  and  more  penetrating  oils.  Heavier 
crude  oils  have  given  satisfactory  results,  even  those  testing  18°  and 
even  lower.  Residiuum  oils  (the  residue  of  crude  petroleum  after  the 
lighter  portions  have  been  distilled  off)  can  be  used  if  natural  crude 
oil  is  unobtainable,  provided  their  content  of  asphaltum  is  not  too  high 
to  prevent  their  emulsification. 

Crude  Oil  Emulsion. 

Formula  18 

Water  to  make  200  gallons 

Liquid  soap  3  gallons 

Natural  crude  petroleum  (21°-24°  Baume)  25  gallons 

Partly  fill  the  spray  tank  with  water,  add  the  liquid  soap,  agitate 
thoroughly  for  one  minute,  add  crude  oil  and  continue  the  agitation 
while  running  in  the  remainder  of  the  water.  If  liquid  soap  cannot  be 
obtained,  use  20  pounds  of  fish  oil  soap  dissolved  in  10  gallons  of  boil- 
ing water  to  which  3  pounds  of  caustic  soda  or  lye  have  been  added. 
To  kill  moss  or  lichens  on  fruit  trees,  add  2  pounds  of  caustic  soda 
or  lye  to  the  formula. 

During  the  spraying  operation  this  emulsion  should  be  thoroughly 
agitated  and  great  care  taken  to  wet  all  of  the  twigs.  From  8  to  10 
gallons  should  be  used  on  a  tree. 

PETROLEUM   DISTILLATES 

Kerosene,  of  about  40°  Baume,  applied  in  the  form  of  an  emulsion, 
has  been  used  to  a  considerable  extent  as  an  insecticide,  particularly 
on  citrus  trees.  The  cheaper,  unrefined  distillates  have  now  largely 
replaced  kerosene  as  a  foliage  spray.  These  are  more  effective  as 
insecticides,  so  that  smaller  percentages  may  be  used  in  the  emulsions, 
but  coupled  with  their  superior  insecticidal  properties  is  their  greater 
toxicity  to  fruit  and  foliage.  The  toxicity  varies  with  climatic  con- 
ditions, foliage  injury  being  most  certain  in  dry  weather  with  a  tem- 
perature of  95°  F.  or  more.  Unfortunately,  the  season  when  spraying 
is  most  effective  against  scale  insects  on  citrus  trees  is  often  during 
the  hottest  and  driest  months.  It  seems  impossible  to  guarantee  im- 
munity from  damage  under  all  conditions  with  any  of  the  distillates 
obtainable. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  83 

Little  injury  to  citrus  fruit  and  foliage  occurs  in  the  coast  regions 
where  distillate  emulsions  have  been  used,  but  in  the  interior  sections 
the  use  of  this  insecticide  is  \ery  hazardous. 

Spraying  with  distillates,  or  with  any  other  material,  is  not  recom- 
mended as  a  substitute  for  fumigation  in  commercial  citrus  orchards, 
except  in  the  case  of  young  orchards,  trees  about  dooryards,  or  where 
fumigation  may  not  be  convenient,  or  infestation  may  be  light  or 
limited  to  occasional  trees.  In  such  cases,  Formula  19  is  considered 
the  most  satisfactory. 

Kerosene  emulsion  is  the  safest  of  the  petroleum-distillate  sprays, 
although  the  most  expensive.  The  "W.  W."  or  "Water  White"  is  a 
trade  name  of  a  low-grade  kerosene  and  is  safer  than  the  usual  grade 
of  material  sold  as  "distillate."  The  highly  refined  "case  goods" 
kerosene  has  been  found  to  cause  the  least  amount  of  injury  of  any  of 
the  petroleum  derivatives,  but  its  cost  is  prohibitive  except  on  a  small 
scale.  If  much  of  the  kerosene  emulsion  is  allowed  to  run  down  the 
trunks  of  young  trees,  injury  is  likely  to  occur  just  beneath  the  surface 
of  the  ground. 

The  following  formula  is  intended  for  use  on  citrus  trees : 

Kerosene  Emulsion. 

Formula  19 

Kerosene   15  gallons 

Liquid  soap %  gallon 

(Or  hard  soap  4  to  12  pounds) 

Water  to  make 200  gallons 

If  liquid  soap  is  available,  it  is  preferable  to  hard  soap,  since  it 
requires  no  heating.  Hard  soap,  preferably  fish  oil  soap,  is  cut  in  thin 
slices  and  dissolved  in  hot  water.  The  soap  is  placed  directly  in  the 
spray  tank  with  10  or  15  gallons  of  water  or  more  (the  exact  amount 
is  not  important)  and  the  engine  then  started.  The  oil  is  now  added 
slowly,  and  the  materials  are  emulsified  by  being  run  through  the 
pump  under  pressure.  After  a  few  minutes  the  rest  of  the  water  may 
be  added,  and  the  spray  is  ready  to  be  applied. 

Certain  "tree"  distillates,  testing  31°  to  32°  Baume,  said  to  be 
selected  and  partially  refined,  have  lately  displaced  to  a  considerable 
extent  the  heavier  distillates  of  27°  to  28°  for  use  on  citrus  trees. 

"Tree"  Distillate  Emulsion. 

Formula  20 

Tree  distillate  (31°-32°  Baume)  4  gallons 

Liquid  soap  %  gallon 

(Or  hard  soap 4  to  12  pounds) 

Water  to  make 200  gallons 


84  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

These  materials  are  emulsified  in  the  manner  explained  for  the 
kerosene  emulsion,  Formula  19.  If  the  distillate  is  used  without 
soap,  the  following  is  the  formula: 

Straight  "Tree"  Distillate. 

Formula  21 

Tree  distillate  (31°-32°  Baume)  4  to  6  gallons 

Caustic  soda  (95  per  cent)  7  pounds 

Water  to  make 200  gallons 

In  the  case  of  the  straight  distillate,  the  oil  is  kept  in  suspension 
in  the  water  by  agitation  and  forms  an  unstable  mechanical  emulsion, 
which  separates  quickly  on  standing.  In  using  this  it  is  necessary  to 
have  the  spray  outfit  equipped  with  a  powerful  and  efficient  agitator, 
which  must  be  kept  going  continuously  during  the  spraying  operation. 

The  use  of  petroleum-distillate  sprays  against  black  scale  on  olive 
trees  is  now  being  recognized  as  profitable.  For  this  purpose  the 
heavier  distillates  of  28°  to  30°  Baume,  being  more  effective,  are  used, 
since  olive  foliage  is  very  resistant  to  spray  injury,  and  also  because 
the  spray  can  be  applied  through  the  winter  months  when  low  temper- 
atures and  high  humidities  are  the  rule. 

Distillates  of  this  density  are  also  much  used  as  a  dormant  spray 
on  deciduous  trees,  although  crude  oil  sprays  are  replacing  distillates 
more  and  more  for  this  purpose. 

Heavy  Distillate  Emulsions. — For  use  on  olives,  the  following 
mechanical  emulsion  is  recommended: 

Formula  22 

Distillate  (28°  Baume)  7  gallons 

Caustic  soda  (95  per  cent)  ...5  to  7  pounds 

Water  to  make 200  gallons 

First  dissolve  the  caustic  soda  in  a  small  amount  of  water  and  add 
to  the  water  in  the  spray  tank ;  begin  the  agitation  and  slowly  add  the 
distillate,  continuing  the  agitation  during  application.  This  spray 
will  also  remove  lichens  or  moss  from  trees. 

If  the  amount  of  crude  oil  is  reduced  from  25  gallons  to  15  gallons 
in  Formula  18,  the  crude  oil  emulsion  may  be  used  on  olive  trees  for 
the  control  of  black  scale. 

For  use  on  dormant  deciduous  trees  the  following  is  recommended : 

Formula  23 

Distillate  27°-28°  Baume)  20  gallons 

Fish  oil  soap   30  pounds 

Water  to  make 12  gallons 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  85 

Dissolve  the  fish  oil  soap  in  water,  heating  it  to  the  boiling  point ; 
add  the  distillate,  and  agitate  thoroughly  while  the  solution  is  hot. 
For  use,  add  20  gallons  of  water  to  each  gallon  of  the  above  mixture. 

Commercial  Prepared  Emulsions  and  Miscible  Oils. — Many  grow- 
ers realize  the  difficulty  in  securing  proper  materials  for  home-made 
emulsions  and  the  variability  of  the  home-made  mixtures  even  under 
the  best  conditions.  They  prefer  to  buy  manufactured  products, 
especially  when  only  small  quantities  are  needed ;  but  the  commercial 
emulsions  and  miscible  oils  are  no  more  effective  than  a  good  home- 
made preparation  and  are  only  more  convenient.  These  preparations 
are  on  the  market  in  great  variety,  many  being  sold  under  trade 
names.  Practically  all  grales  of  petroleum  distillates,  as  well  as  crude 
petroleum,  are  obtainable  in  a  form  ready  to  be  used,  after  simple 
dilution  with  water.  If  these  ready-made  preparations  are  to  be 
used,  it  is  especially  important  to  purchase  only  from  reliable  and 
well-known  manufacturers  or  dealers.  The  commercial  products  in 
general  are  satisfactory  for  use  for  the  purposes  indicated  for  the 
above  formulas. 

The  following  is  recommended  for  the  control  of  thrips: 

Distillate  Emulsion  and  Tobacco  Extract. — Government  formula. 

Formula  24 

The  government  formula  for  the  control  of  pear  thrips  is  the 
following : 

Distillate  emulsion 10  gallons 

Nicotine  sulfate  40  per  cent 1  pint 

Water  to  make 200  gallons 

"When  this  formula  was  first  prepared  there  were  few  commercial 
oil  sprays  on  the  market,  so  that  it  was  necessary  first  to  make  a  dis- 
tillate emulsion  (Formula  23),  In  recent  years  there  have  appeared 
the  miscible  oils,* which  may  be  used  as  follows: 

Formula  24a 

Miscible  oil  5  gallons 

Nicotine  sulfate  40  per  cent 1  pint 

Water  to  make 200  gallons 

These  formulas  are  for  use  against  the  adult  ' '  black  thrips, ' '  and 
should  be  applied  liberally  as  soon  as  any  considerable  number  of  in- 
sects are  found  upon  the  trees.  Do  not  fail  to  make  daily  inspections 
after  the  buds  begin  to  swell.  Applications  should  be  repeated  if 
necessary  until  the  adults  begin  to  lessen  in  numbers. 


86  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

In  case  the  "  white  thrips"  appear  in  destructive  numbers  later, 
the  same  formula  may  be  safely  used  if  the  oil  content  is  decreased 
and  the  nicotine  increased  as  follows: 

Formula  24& 

Distillate  emulsion 6  gallons 

Nicotine  sulfate  40  per  cent 1%  pints 

Water  to  make 200  gallons 

Formula  24c 

Miscible  oil  3  gallons 

Nicotine  sulfate  40  per  cent 1%  pints 

Water  to  make 200  gallons 

For  work  with  thrips,  the  greater  force  and  volume  delivery  of  the 
spray  gun  has  rendered  it  superior  to  the  spray  rod,  insuring  not  only 
a  better  but  a  quicker  and  easier  job.  The  loss  in  material  is  more 
than  overcome  by  the  rapidity  and  ease  of  operation. 

The  resin  wash  is  chiefly  used  for  young  and  tender  nursery  stock, 
because  it  does  not  cause  the  injury  often  following  the  application 
of  petroleum  distillates.     The  preparation  is: 

Formula  25 

Resin  10  pounds 

Caustic  soda  (76  per  cent  to  95  per  cent) 3  pounds 

Fish  oil iy2  pounds 

Water  to  make  50  gallons 

To  a  gallon  of  hot  water  in  an  iron  kettle  add  the  fish  oil  and  the 
resin,  and  heat  until  the  latter  is  softened.  After  first  dissolving  the 
caustic  soda  in  a  small  quantity  of  water  add  it  and  stir  the  mixture 
thoroughly.  After  this  pour  in  enough  water  to  make  50  gallons  of 
spray  material. 

Crude  Carbolic  Acid  Emulsion. — For  citrus  trees. 

Formula  26 

Fish  oil  soap  40  pounds 

Crude  carbolic  acid  5  gallons 

Water  to  make 40  gallons 

Dissolve  the  soap  completely  in  hot  water,  add  the  carbolic  acid 
and  heat  to  the  boiling  point  for  twenty  minutes  (reserve  some  water 
to  add  in  case  the  mixture  begins  to  boil  over.)  For  use,  add  20 
gallons  of  water  to  every  gallon  of  the  above  solution.  The  emulsion 
needs  little  or  no  agitation. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  87 

CRUDE  CARBOLIC  ACID  AND  DISTILLATE  EMULSION 

Formula  26a 

Fish  oil  soap  (or  liquid  soap,  5  gallons)  40  pounds 

Crude  carbolic  acid  (25  per  cent)  5  gallons 

Distillate  27°-28°  Baume)  5  gallons 

Water  to  make 50  gallons 

Prepare  as  with  Formula  26,  adding  the  distillate  after  the  crude 
carbolic  acid.  This  mixture  is  specially  recommended  for  mealybugs 
on  dormant  deciduous  fruit  trees.     Dilute  1  to  20  for  use. 

Formula  265 

Coal  Tar  Creosote  Dip. — Coal  tar  derivatives  which  may  be  creosote 
oil,  crude  carbolic  acid  or  cresylic  acid  emulsified  by  means  of  soap 
are  also  used.  These  are  sold  under  various  trade  names  and  should 
be  used  according  to  directions.  The  requirement  which  has  been 
made  for  such  dips  by  the  United  States  Department  of  Agriculture 
is  that  when  diluted  for  use  they  shall  contain  "one  per  cent  by 
weight  of  coal-tar  oils  and  cresylic  acid.  In  no  case  should  the  diluted 
dip  contain  more  than  four-tenths  of  one  per  cent  nor  less  than  one- 
tenth  of  one  per  cent  of  cresylic  acid.'' 

These  preparations  cannot  be  used  in  very  hard  water  except 
by  a  preliminary  water  softening.  Hard  water  may  be  softened 
by  dissolving  lye  at  the  rate  of  12  ounces  of  high-grade  concentrated 
lye  to  100  gallons  of  water ;  then  add  the  dip. 

If  the  emulsion  still  breaks  or  forms  in  globules  after  treatment 
with  lye  it  will  be  necessary  to  use  lime-sulfur  solution  or  an  arsenical 
dip. 

TOBACCO  PREPARATIONS 

Concentrated  commercial  preparations  of  tobacco  have  almost  en- 
tirely superseded  the  home-made  tobacco  infusions  on  account  of  their 
greater  convenience  and  uniformity.  A  material  containing  40  per. 
cent  nicotine  in  the  form  of  nicotine  sulfate  is  recommended  for  the 
preparation  of  contact  insecticides  containing  nicotine.  The  usual 
formula  is: 

Formula  27 

Tobacco  extract  (nicotine  sulfate,  40  per  cent 1  pint 

Fish  oil  soap , 4  to  5  pounds 

Water 100  to  150  gallons 

For  small  quantities,  use  1  teaspoonful  to  1  gallon  of  water. 


88  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Formula  27a 

Nicotine  sulfate,  40  per  cent 1  pint 

Dry  billboard  paste 2  pounds 

Water 150  gallons 

Make  a  paste  of  the  dry  material  and  add  it  to  the  water  and  nico- 
tine. This  spray  is  intended  for  plants  like  potatoes,  tomatoes,  etc., 
which  are  sensitive  to  soap  mixtures. 

Tobacco  Dust. — Finely  ground  tobacco  dust  finds  some  use  as  an 
insecticide,  particularly  in  the  control  of  aphids.  Fifty  per  cent  of 
kaolin  or  hydrated  lime  is  sometimes  mixed  with  it  as  a  diluent. 

NICODUST  AND  COMBINATIONS 

Nicodust,  invented  and  named  by  Professor  Ralph  E.  Smith,  is 
composed  of  a  carrying  substance,  like  finely  powdered  kaolin  or  lime, 
treated  with  a  concentrated  solution  of  nicotine  sulfate,  commercially 
known  as  " Nicotine  Sulfate  40  per  cent."  The  nicotine  in  such  com- 
bination, especially  with  lime,  becomes  very  volatile  and  is  quickly 
driven  off  by  heat.  In  this  form  therefore  it  acts  largely  as  a  fumi- 
gant,  but  may  be  effective  as  a  contact  poison  as  well.  As  soon  as 
mixed,  the  dust  should  be  packed  in  air-tight  containers  to  retain 
the  nicotine  content.  The  best  results  in  killing  insects  have  been 
secured  when  the  temperature  is  over  70°  F.,  and  very  poor  results 
have  followed  its  use  in  cold  weather.  The  various  strengths  are 
usually  denoted  by  the  amount  of  "Nicotine  Sulfate  40  per  cent" 
contained,  as  follows:  2  per  cent  "Nicotine  Sulfate  40  per  cent," 
4  per  cent,  5  per  cent,  6  per  cent,  10  per  cent,  etc.  A  statement  of 
the  actual  amount  of  nicotine  is  more  accurate  and  is  required  in 
the  guarantee  of  commercial  preparations. 

The  name  nicodust  does  not  belong  exclusively  to  any  particular 
mixture  or  company,  but  was  originated  as  a  convenient  name  for  all 
mixtures  of  this  sort. 

Arsenate  of  lead  and  sulfur  are  mixed  with  nicodust  at  the  time  of 
manufacture  and  give  convenient  combinations  for  treating  different 
types  of  insects  or  insects  and  fungus  diseases  at  one  application. 
Sulfur-nicodust,  under  actual  field  tests,  appears  to  be  more  efficient 
in  killing  insects  than  ordinary  nicodust  containing  the  same  percent- 
age of  "Nicotine  Sulfate  40  per  cent."  Thus  in  the  control  of  the 
rosy  apple  aphis,  a  sulfur-nicodust  containing  50  per  cent  of  sulfur, 
6  per  cent  of  "Nicotine  Sulfate  40  per  cent,"  and  44  per  cent  of 
inert  material  gave  far  better  results  than  a  6  per  cent  nicodust. 


Circular  265]  plant  disease  AND  PEST  CONTROL  89 

The  strengths  commonly  used  are  2  per  cent  nicodust  for  walnut 
aphis  and  cherry  or  pear  slug,  5  or  6  per  cent  for  most  of  the  aphids, 
thrips,  etc.,  and  a  10  per  cent  dust  for  the  more  resistant  aphids  such 
as  the  pea  aphis.  Nearly  all  of  the  hairy  caterpillars,  such  as  the  tent 
caterpillars,  webworms,  thistle  butterfly  larvae,  as  well  as  the  velvety 
cabbage  worms,  to  which  the  nicodust  adheres  readily,  are  easily  killed 
with  a  6  per  cent  dust  if  applied  while  the  caterpillars  are  quite  young. 
Smooth  caterpillars,  like  cutworms,  on  the  other  hand,  do  not  readily 
succumb  to  any  ordinary  treatment  with  the  material.  Insects  which 
are  protected  with  a  waxy  or  cottony  material,  like  the  woolly  apple 
aphis,  the  mealy  plum  louse,  mealybugs,  etc.,  are  not  susceptible  to 
nicodust  at  all,  while  those  which  have  a  wet  or  slimy  covering,  like 
the  cherry  or  pear  slug,  or  glandular  hairs,  like  the  walnut  aphis,  are 
easily  killed  with  very  weak  nicotine  contents. 

Recently,  machines  for  mixing  and  applying  the  materials  at  the 
same  time  have  been  devised.  These  promise  increased  efficiency  and 
economy  in  some  large-scale  operations.  (See  University  of  Calif- 
ornia Bulletin  No.  357.) 

Hydrocyanic  Acid  Gas. — The  most  effective  fumigant  in  common 
use,  but  on  account  of  its  danger  to  the  operator  should  if  possible 
be  used  only  under  expert  supervision.  The  gas  is  lighter  than  air, 
diffusing  upward  very  rapidly,  hence  the  danger  to  occupant  of 
upper  or  adjoining  rooms.  The  danger  of  explosion  and  fire  from 
the  use  of  carbon  bisulfid  is  practically  eliminated  with  this  gas. 

Vacuum  fumigation  with  this  and  other  gases  where  possible  is 
more  successful  than  that  in  improvised  fumigating  rooms. 

The  gas  is  generated  by  adding  the  cyanid  to  a  solution  of  sul- 
furic acid. 

The  amount  of  sodium  cyanid  required  for  a  tightly  built  room 
is  1%  ounces  per  100  cubic  feet,  the  chemicals  being  used  in  the  follow- 
ing proportions: 

Sodium  cyanid  1%  pounds 

Sulfuric  acid 2%  pints 

Water 3  pints 

A  room,  10  x  16  x  10  feet,  contains  1600  cubic  feet  and  would 
require  1%  pounds  of  sodium  cyanid,  2%  pints  (66  ounces  by  weight) 
of  sulfuric  acid,  and  3  pints  of  water.  The  proportions  for  the  chem- 
icals given  should  not  vary,  but  the  amount  used  per  hundred  cubic 
feet  must  be  determined  according  to  the  tightness  of  the  room.  The 
above  amount  of  cyanid  may  be  reduced  one-third  in  a  room  built 
especially  for  fumigating  purposes,  with  a  corresponding  change  in 


90  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

the  amounts  of  acid  and  water.     Twice  the  above  dosage,  or  even  more, 
should  be  used  for  buildings  of  only  approximate  tightness. 

Liquid  hydrocyanic  acid  gas  is  now  used  for  citrus  orchard  fumi- 
gation. For  full  directions  consult  the  local  county  agent  or  horti- 
cultural officers. 

MISCELLANEOUS 

Carbon  Tetrachloride. — This  may  be  substituted  for  carbon  disul- 
fid  in  household  fumigation  by  using  it  in  the  same  manner  and 
slightly  increasing  the  amount  used.  It  is  non-inflammable  and  con- 
sequently safer  than  carbon  disulfid,  while  its  lower  toxicity  makes  it 
safer  for  the  operator. 

Corrosive  Sublimate  (Bichlorid  of  Mercury  or  Mercuric  Chlorid). 
— This  is  a  very  poisonous  substance  and  is  one  of  the  most  powerful 
of  germicides ;  it  is  employed  to  some  extent  in  plant  disease  treatment. 
The  usual  strength  is : 

Formula  28 

Corrosive  sublimate  1  ounce 

Water   8  gallons 

Or  1  part  to  1000. 

Tablets  to  make  this  strength  when  added  to  1  pint  of  water  may 
be  obtained  at  drug  stores.  Distilled  or  rain  water  should  be  used; 
the  solution  must  not  be  kept  in  a  metal  container.  It  is  also  quickly 
spoiled  by  contact  with  clay  or  an  organic  substance  such  as  the  cut 
surfaces  of  potatoes. 

Another  formula  is  recommended  by  Mr.  C.  F.  Reimer  for  dis- 
infecting tools  and  cuts  in  pear  blight  control  work.  It  will  probably 
be  found  superior  to  Formula  28  for  general  tree  work  of  this  kind. 
It  is: 

Formula  28a 

Corrosive  sublimate  1  ounce 

Mercuric  cyanid 1  ounce 

Water  4  gallons 

Or  1  part  of  each  ingredient  to  500. 

Whitewash. 

Formula  29 
(Ordinary  Formula) 

Water  2  gallons 

Quicklime  10  pounds 

Add  more  water  after  slaking  to  bring  the  wash  to  the  desired 
consistency. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  91 

A  more  durable  whitewash : 

Formula  30 

Quicklime  5  pounds 

Salt  %  pound 

Sulfur  %  pound 

Slake  the  lime  slowly  with  water  and  add  the  salt  and  sulfur  while 
it  is  boiling.  Add  enough  more  water  to  make  a  good  wash.  This  is 
good  for  whitewashing  the  bodies  of  trees  in  the  fall.  In  localities 
where  there  are  deer  this  whitewash  is  not  recommended,  as  the  deer 
are  said  to  be  attracted  by  the  salt  it  contains  and  injure  the  trees. 

Government  Whitewash. 

Formula  31 

Quicklime  40  pounds 

Salt  15  pounds 

Rice  flour  3  pounds 

Spanish  whiting  V2  pound 

Glue    1  pound 

Water  5  gallons 

Grafting  Wax. — Many  different  combinations  are  used  for  this 
purpose,  most  of  them  being  various  combinations  of  beeswax  and 
resin.      The  following  formula  is  a  good  one: 

Formula  32 

Resin  4  pounds 

Beeswax   1  pound 

Linseed  oil  1  pint 

The  ingredients  are  all  melted  and  mixed  together  in  a  kettle.  In 
hot  weather  use  more  resin. 

Some  use  one  pound  of  tallow  as  a  substitute  for  the  linseed  oil. 
One  ounce  of  lampblack  or  one  pint  of  flour  is  sometimes  added. 
Asphaltum  is  used  to  some  extent  as  a  substitute  for  resin  and  bees- 
wax, and,  in  fact,  straight  asphaltum  is  used  successfully  in  some  cases 
for  grafting  wax. 

Carbon  Disulfid. — A  liquid  which  evaporates  quickly  when  ex- 
posed to  the  air,  forming  a  heavy  and  inflammable  vapor  of  great 
penetrating  power.  In  using  the  material  for  fumigation,  it  is  essen- 
tial that  it  be  placed  near  the  top  of  the  chamber  in  a  shallow  container 
in  order  that  the  heavy  vapors  as  they  are  given  off  may  thoroughly 
diffuse  through  the  air  contained  in  the  space  to  be  fumigated.  The 
proper  amount  to  use  depends  upon  the  type  of  room  being  fumigated 
and  ranges  from  10  pounds  to  about  30  pounds  to  1000  cubic  feet  in 


92  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ordinary  rooms  where  the  walls  and  floor  have  not  been  made  especially 
tight.  The  best  results  are  obtained  by  doing  this  work  when  the 
temperature  is  above  70°  F. 

Carbon  disulfid  is  one  of  the  best  agents  for  destroying  ground 
squirrels  that  have  failed  to  take  poisoned  grain,  or  having  once  sur- 
vived the  poison  refuse  to  take  it  again.  It  is  most  effective  if  used 
during  the  winter  season  when  the  ground  is  wet.  The  best  methods 
of  applying  it  are  by  the  use  of  the  "waste-ball"  and  of  the  "de- 
structor pump."  The  common  waste-ball  method  is  to  pour  a  table- 
spoonful  of  carbon  disulfid  on  a  piece  of  cotton  waste,  corncob,  horse 
manure,  or  other  absorptive  material,  and  then  to  throw  this  as  far 
down  the  hole  as  possible,  closing  the  opening  immediately  with  earth. 
Exploding  the  gas  with  a  torch  before  closing  the  opening  is  recom- 
mended where  the  ground  is  damp  and  there  is  no  danger  of  fire.  The 
explosion  of  gas  forms  new  compounds  which  are  poisonous  and  may 
diffuse  somewhat  more  rapidly  than  the  vapors  of  the  material.  The 
"destructor"  pumps  the  vaporized  carbon  bisulfid  into  the  burrow, 
and  is  said  to  be  as  effective  as  exploding  the  gas. 

Poisoned  Barley  or  Strychnine-coated  Barley. — Following  is  the 
latest  government  formula  for  preparing  poisoned  barley  for  Calif- 
ornia ground  squirrels. 

Formula  33 

Barley  (clean  grain)  16  quarts 

Strychinine  (powdered  alkaloid)  1  ounce 

Bicarbonate  of  soda  (baking  soda)  1  ounce 

Thin  starch  paste %  pint 

Heavy  corn  syrup  %  pint' 

Glycerin 1  tablespoonful 

Saccharin    1/10  ounce 

Mix  thoroughly  1  ounce  of  powdered  strychnine  (alkaloid)  and 
1  ounce  of  common  baking  soda.  Sift  this  into  %  pint  of  thin,  hot 
starch  paste  and  stir  to  a  smooth,  creamy  mass.  (The  starch  paste 
is  made  by  dissolving  1  heaping  tablespoonful  of  dry  gloss  starch 
in  a  little  cold  water,  which  is  then  added  to  %  pint  of  boiling  water ; 
boil  and  stir  constantly  until  a  clear,  thin  paste  is  formed.)  Add 
14  pint  of  heavy  corn  syrup  and  1  tablespoonful  of  glycerin  and 
stir  thoroughly.  Add  Vio  ounce  of  saccharine  and  stir  thoroughly. 
Pour  this  mixture  over  16  quarts  of  clean  barley  and  mix  well  so  that 
each  grain  is  coated. 

Caution. — All  containers  of  poison  and  all  utensils  used  in  thq^ 
preparation  of  poisons  should  be  kept  PLAINLY  LABELED  and 
OUT  OF  REACH  of  children,  irresponsible  persons,  and  live  stock. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  93 

Formula  34 

Poisoned  Vegetables  for  Gophers 

Sweet  potatoes,  parsnips,  or  carrots  (cut  in  %"  cubes) 4  quarts 

Flour  paste  *4  pint 

Strychnine  alkaloid,  powdered ~  %  ounce 

Saccharin 1/32  ounce 

SPREADERS 

Spreaders  are  often  added  to  sprays  to  give  them  a  more  even  dis- 
tribution over  the  surface  of  the  leaves  and  to  prevent  them  from 
collecting  into  drops.  Some  of  them  also  have  insecticidal  value  and 
others  act  as  adhesives.  So  much  is  claimed  for  these  materials 
which  is  not  fully  warranted  that  many  persons  have  come  to  feel 
that  none  should  be  recommended.  However,  the  advantages  gained 
should  not  be  entirely  overlooked,  and  we  include  here  some  of  the 
more  important  substances  used  for  these  purposes. 

Casein. — This  is  a  comparatively  new  material  for  use  as  a  spreader 
and  adhesive  in  sprays.  It  is  a  dry  product  which  readily  mixes 
in  cold  water  and  is  put  up  in  small  or  large  containers.  One  and 
one-half  pounds  are  sufficient  for  200  gallons  of  the  diluted  spray. 
Casein  is  soluble  only  in  alkaline  solutions  and  is  therefore  worth- 
less in  acid  insecticides  and  fungicides  which  are,  however,  seldom 
used. 

Flour  Paste,  Billboard  Paste. — These  materials  are  excellent 
spreaders  and  act  as  adhesives  as  well.  They  may  be  used  with  safety 
in  all  sprays,  because  they  give  no  chemical  reactions.  Flour  paste 
and  certain  of  the  dry  billboard  and  paperhanger 's  pastes  should  be 
mixed  in  a  small  quantity  of  hot  water  before  adding  to  the  spray 
tank.  They  are  somewhat  difficult  to  handle.  A  specially  prepared 
billboard  and  paperhanger 's  paste,  known  as  " steamed  paste,"  is 
already  cooked,  and  as  a  wet  paste  mixes  readily  with  cold  water. 
It  may  be  obtained  in  barrel  lots  or  in  small  quantities  from  paint  and 
paper  dealers.     The  amounts  to  be  used  are  as  follows : 

Flour  (cheap  grade),  2  to  4  pounds  to  200  gallons  of  dilute  spray 

material. 
Dry  billboard  paste,   2   pounds  to   200   gallons  of   dilute  spray 

material. 
Steamed  paste,  4  pounds  to  200  gallons  of  dilute  spray  material. 


94  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Glue. — As  a  spreader  and  adhesive,  glue  has  long  been  used  in 
sprays,  and,  like  the  flour  pastes,  may  be  used  in  all  kinds  of  materials. 
Two  ounces  of  dry  glue  dissolved  in  hot  water  are  sufficient  for  200 
gallons  of  diluted  sprays. 

Oil  Emulsions  and  Miscible  Oils. — Because  of  their  penetration, 
these  materials  are  often  of  value  in  carrying  other  materials,  like 
nicotine.  They  should  be  used  sparingly,  about  2  gallons  to  200 
gallons  of  diluted  spraying  materials.  When  so  diluted  they  have 
little  value  except  as  spreaders. 

Resin-fish  oil  soap  (see  Formula  10a)  is  often  used  with  Bordeaux 
mixture.  It  is  somewhat  tedious  to  prepare  and  may  now  be  pur- 
chased ready  to  use.  This  is  very  similar  in  character  to  the  resin 
wash  (see  Formula  25). 

Soap. — This  is  one  of  the  oldest  and  best  known  spreaders  and  is 
often  used  in  sprays  for  this  purpose  as  well  as  for  an  emulsifier  and 
insecticide.  As  a  spreader  for  such  materials  as  arsenate  of  lead, 
for  codling  moth,  use  4  to  12  pounds  of  fish  oil  soap  to  200  gallons 
of  diluted  spray  material. 


HEAT  AS  AN  INSECTICIDE 

A  temperature  of  130°  F.,  as  far  as  records  go,  if  prolonged  for 
several  hours,  will  kill  all  forms  of  insect  life.  This  temperature 
can  readily  be  obtained  in  well-built  buildings  which  are  connected 
with  a  steam  plant.  The  first  expense  of  installing  radiators  is  con- 
siderably more  than  fumigation  with  chemicals,  but  after-treatments 
are  very  much  cheaper  and  without  danger  to  the  operators  or  to  the 
contents  of  the  building. 

Higher  temperatures  of  145°  to  180°  F.  have  been  reported  as 
successful  in  a  much  shorter  period  of  time  than  the  first  figure  men- 
tioned. The  desired  degree  of  heat,  however,  must  be  obtained 
throughout  the  entire  mass  which  is  being  treated,  it  not  being  suf- 
ficient to  heat  the  room  alone  to  145°  or  more.  Small  amount  of 
provisions  or  woolen  cloths  infested  with  moths  may  be  heated  for 
thirty  or  forty  minutes,  in  the  oven  of  an  ordinary  cook  stove,  care 
being  taken  to  avoid  scorching  heat.  A  temperature  high  enough  to 
slightly  brown  a  white  paper  bag  will  be  found  about  right.  The 
use  of  a  smoothing  iron  just  hot  enough  not  to  scorch  will  kill  the 
larvae  of  clothes  moths  while  in  the  cloth,  but  other  measures  must 
be  taken  to  reach  the  adult  insects. 


Circular  265]  PLANT  DISEASE  AND  PEST  CONTROL  95 


SOIL  DISINFECTION 

For  the  prevention  of  damping  off  and  of  many  specific  soil-borne 
infections,  treatment  may  be  practical  in  cases  such  as  seedbeds, 
greenhouse  soil  or  where  limited  amounts  of  material  are  to  be  dealt 
with.  Plants  at  first  are  slightly  retarded,  but  soon  grow  with  in- 
creased vigor  in  properly  disinfected  soils. 

Steam  Cooking  is  generally  considered  the  most  effective  method 
of  soil  treatment  for  the  above  purposes  and  various  devices  have 
been  employed  for  doing  the  work.  A  system  of  1%  incn  pipes  may 
be  laid  18  inches  apart  and  1  foot  below  the  surface.  These  pipes 
should  be  perforated  on  their  lower  sides  with  i/^-inch  holes  at  in- 
tervals of  6  inches  and  should  be  supplied  with  steam  at  a  pressure 
of  80  to  150  pounds  pressure.  The  soil  should  be  covered  with 
blankets  before  the  steam  is  admitted,  and  potatoes  buried  in  different 
places  in  the  soil.  After  treatment  for  an  hour,  the  potatoes  may  be 
examined  and  if  cooked,  the  treatment  may  be  considered  effective. 
The  soil  may  be  used  in  place  or  may  be  removed  to  clean  benches 
or  beds,  using  care  not  to  again  contaminate  it.  Benches,  frames, 
etc.  should  be  drenched  with  boiling  water  or  formaldehyde  solution 
before  use.     See  below. 

The  Inverted-Pan  Method  consists  in  admitting  steam  below  an 
inverted  galvanized  iron  pan,  furnished  with  handles  for  moving, 
and  which  is  pressed  down  to  confine  the  steam.  A  size  of  6'  x  8', 
and  6  inches  deep  has  been  recommended.  Injurious  insects,  fungi, 
nematodes  and  weed  seed  are  destroyed  by  steam  cooking  and  it  has 
been  reported  in  some  cases  that  the  cost  has  not  been  greater  than 
that  of  weeding  untreated  soil. 

Surface  Firing. — Brush  is  frequently  piled  on  seedbeds  prepared 
for  sowing  and  burned.  Seed  is  sown  as  soon  as  possible  with  a 
minimum  stirring  of  the  surface.  The  effect  in  this  case  is  very 
superficial. 

Formaldehyde  Treatment. — Formaldehyde  may  be  used  on  seed- 
beds prepared  to  sow.  The  soil  may  be  soaked  with  a  solution  of 
1  pound  of  formalin  in  6  gallons  of  water.  The  soil  should  be  kept 
covered  for  a  day  and  allowed  to  stand  for  a  week  before  sowing. 

Hot  Water  Treatment. — Considerable  benefit  may  be  derived  from 
drenching  the  soil  with  boiling  water.  Empty  pots,  flats,  pots  with 
soil,  and  implements  may  be  immersed  in  boiling  water  for  five 
minutes. 


96  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


WEED  KILLERS,  TREE  KILLERS 

Salt. — Common  salt  may  be  applied  on  walks  or  similar  places 
where  it  is  desired  to  prevent  the  growth  of  all  vegetation.  In  the 
studies  of  barberry  eradication  it  was  found  that  10  pounds  of  com- 
mon salt  poured  about  the  base  of  the  large  shrubs  was  one  of  the 
surest  means  of  eradication.  Soil  with  which  the  salt  comes  in  con- 
tact is  injured  for  growing  plants. 

Sodium  Arsenite. — See  p.  73.  This  is  one  of  the  most  widely 
used  of  weed  killers.  Sprayed  on  foliage  or  the  soil  it  is  very 
destructive  to  vegetation.  Like  common  salt,  it  permanently  injures 
soil  where  applied  in  considerable  quantity.  1  pound  of  the  arsenic  in 
10  to  25  gallons  of  water  may  be  sprayed  on  soil  or  foliage.  For 
killing  trees,  use  1  pound  to  2  gallons  of  water,  girdle  the  tree  by 
downward  strokes  of  the  axe  and  pour  about  1  pint  to  1  quart  of 
the  solution  into  the  cuts.  This  is  a  dangerous  poison  whether  to 
handle,  to  get  on  fodder,  or  to  inhale  its  fumes  when  preparing  it. 

Carbon  Disulfid. — For  killing  morning  glory,  apply  in  dry  soil 
in  holes  18  inches  deep  and  3  feet  apart  each  way.  Put  4  ounces  of  the 
liquid  in  each  hole  and  cover.  This  does  not  permanently  injure  the 
soil.    See  also  under  "Lawns,"  p.  31. 


Circular  265] 


PLANT  DISEASE  AND  PEST  CONTROL 


97 


INDEX 


Acanthoscelides  obtectus  Say,  13. 

Achemon  sphinx  moth,  29. 

Actinomyces  scabies  (Thaxter)  Giiss., 
45. 

Aegeria  opalescens  Hy.  Edw.,  37. 

Aegeria  rutilans  H.  Edw.,  48. 

Aegeria  tipuliformis  Clerck.,   24. 

Angumoise  grain  moth,  22,  28. 

Alfalfa,  1. 

Alfalfa   caterpillar,   2. 

Alkali  sulfides,  79. 

Almond,  3. 

Almond  mite,  3. 

Ammoniacal  solution  of  copper  car- 
bonate,  76. 

Anarsia   lineatella   Zeller,    37. 

Anasa  tristis  De  Geer,  32. 

Anthraenose   (bean),  12. 

Ants,  60. 

Ant  Syrup,  Government  Argentine, 
74. 

Ant  syrups,  73. 

AnurapMs  roseus  Baker,  5. 

Aphids  (celery),  17;  (chrysanthe- 
mum) 19,  (citrus)  21,  (grain) 
28,  (potato)  45,  (rose)  46,  (snap- 
dragon)  47. 

Aphis — Artichoke,  11;  Bean  (bean), 
13,  (dahlia)  25;  Black  cherry, 
18;  brassicae  Linn.,  16;  Cabbage, 
16;  Green  apple  (apple),  5, 
(loquat)  31,  (pear)  41;  Hop,  30; 
Melon  (cucumber)  24,  (melon) 
32,  (spinach)  48;  Pear  root,  41; 
pomi  De  Geer,  5;  Rosy,  5; 
rumicis  Linn.,  13 ;  Strawberry,  48 ; 
Walnut,  52;  Woolly  apple,  6. 

Apoplexy   (grape),  29. 

Apple,  4. 

Apricot,  7. 

Archips  argyrospila  Walker,  5. 

Armillaria  (almond)  3,  (apricot)  7, 
(cherry)  18,  (olive)  33,  (peach) 
36,  (plum,  prune)  42,  (walnut) 
51. 

Armillaria  mellea  (Vahl.)  Quel.,  53. 

Armillaria  root  rot  (citrus)  20,  53. 

Armyworms  (alfalfa)  2,  (beet)  14, 
(cabbage)  16,  (citrus)  21,  (corn) 
22,  (grain)  28,  (grape)  29, 
(onion)  34,  (pea)  35,  (potato) 
45,  (sorghum,  etc.)  47,  (spinach) 
48,    (tomato),  51,  53. 

Arsenate  of  lead  (with  nicodust), 
88. 


Arsenic,  trioxide,  71. 

Arsenic,  White,  71. 

Arsenical  dip,  Government,  71. 

Arsenicals,   70. 

Artichoke,  10. 

Ascaris  lumbricoides  Linn.,  67. 

Asparagus,  11. 

Aspidiotus   hederae  Vail.,   34. 

Aspergillus  niger  V.  Tiegh.,  26. 

Aspidiotus  perniciosus   Comst.,    6. 

Aulacaspis  rosae  (Bouche),  16. 

Avocado,  11. 

Bacillus  amylovorus  (Burr.)  De  T. 
(apple)  4,  (loquat)  31,  (pear)  39. 

Bacterial  gummosis — See   Gummosis. 

Bacteriosis  (pea),  35. 

Bacterium  cerasi  Griffin,  7. 

Bacterium  citriputiale,   19. 

Bacterium  savastanoi  E.  F.  Smith,  33. 

Bacterium  tumefaciens  S.  &  T.  (bush 
fruits)    15,   (grape)   28,  55. 

Barley,   26. 

Bean,  12. 

Bed  bugs,  60. 

Beeswax,  91. 

Beet,   13. 

Beetle — Bark  (apricot),  10;  Dried 
fruit,  (date)  25,  (prune)  43, 
(raisin)  29;  Fruit  tree  bark  (avo- 
cado), 12;  Fuller's  rose  (citrus), 
22,  (rose)  47;  Olive  bark,  34; 
Rose  snout,  47;  Strawberry  flea, 
49;    Strawberry   leaf,   49. 

Beetles — Darkling  ground  (tomato), 
51;  Flea  (cucumber)  23,  Hop, 
30,  (melon)  32,  (potato)  45, 
(spinach)  48,  Strawberry,  49, 
(tomato)  51;  Leaf  (potato),  45; 
Striped  cucumber  (cucumber),  24, 
(melon)  32;  Twelve-spotted  cu- 
cumber (cucumber),  24,  (dahlia) 
25,    (melon)   32. 

Belascarius   marginata   Rud.,    66. 

Bichlorid  of  mercury,  90. 

Billboard  paste,   93. 

Bitter  pit  (olive),  33,  57. 

Blackberry,   15. 

Black  end  (pear),  39. 

Black  heart  (apricot)  7,  (potato)  44. 

Black  knot  (grape),  28. 

Black  leaf  (pear),  39. 

Black  measles  (grape),  29. 

Black  pit  (citrus),  19. 

Black  scale  (olive)  33,  (peach)  37. 

Black  scurf  (potato),  44. 


98 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 


Blapstinus  sp.,  51. 

Blast   (citrus),  19. 

Blight  (apple),  4;  Bacterial  (pea), 
35;  (beet)  13;  Bud  (apricot),  8, 
(camellia)  17;  Cane,  15;  (celery) 
17;  Late  (tomato),  50;  (pea)  35; 
Peach  (apricot),  8,  (peach),  36; 
Pear  (loquat),  31,  (pear)  39; 
Potato  late,  44;  Twig  (apricot), 
9,  (walnut)  51;  Western  (to- 
mato), 50. 

Blue  mold  (citrus),  20. 

Bluestem,  15. 

Bluestone,  75. 

Bordeaux  mixture  (average  strength), 
74;  Commercial,  75;  Eesin,  75. 

Bordeaux  paste,  74. 

Borer,  Branch  and  twig  (apricot),  9, 
(avocado)  12,  (fig)  26,  (olive) 
33,  (peach)  37,  (pear)  40,  (plum, 
prune),  42. 

Borer,  California  peach  (almond),  3, 
(apricot)  10,  (cherry)  18,  (peach) 
37,  (plum,  prune)  42. 

Borer,  Flat-headed  apple-tree  (apple) 
5,  (currant,  gooseberry)  24, 
(peach)  37,  (plum,  prune)  43. 

Borer,  Imported  currant,  24. 

Borer,  Nautical,  52. 

Borer,  Peach  twig  (almond)  3,  (apri- 
cot) 10,  (peach)  37,  (plum, 
prune)  43. 

Borer,  Potato  stalk,  46. 

Borer,  Shot  hole  (apricot)  10,  (peach) 
38. 

Borers,  Flat-headed,  81. 

Botrytis,  15. 

Botrytis  cinerea,  26. 

Bran  mash,  Citrus,  72;  Poison,  72. 

Bromius  obscurus  (Linn.),  29. 

Broom  corn,  47. 

Brown  rot  (apricot),  8,  (peach)  36, 
(plum,  prune)  42. 

Brown  rot  of  lemon  (citrus)  20, 
(nursery  stock)   33. 

Brown  streak  (potato),  44. 

Bruchus  pisorum  Linn.,  35. 

Bruchophagus  funebris  How.,  2. 

Bryobia  praetiosa  Koch.,  3. 

Bucculatrix  thurberiella  Busck.,  23. 

Bugs,  Tule  or  stink,  62. 

Bush  fruits,   15. 

Butterfly,  The  painted  lady,  30. 

Cabbage,  16. 

Calandra  granaria  Linn.,  28. 

Calandra  oryzae  Linn.,  28. 

Caliroa  cerasi  (Linn.),  19. 

Camellia,  17. 

Canker,  Pythiacystis    (avocado),   11. 


Cankerworms    (apple),    6,    (apricot) 

10,  (peach)  37,  (pear)  40,  (plum, 

prune),  42,  54. 
Cantaloupe,  31. 
Carabidae,  54. 

Carbolic  acid  emulsion,  Crude,  86. 
Carbolic  acid,    Crude,    and   distillate 

emulsion,  87. 
Carbon  disulfid,  28,  90,  91,  96. 
Carbon  tetrachloride,  90. 
Carpophilus  hemipterus  (Linn.),  43. 
Casaba,  31. 
Casein,  93. 

Caterpillar,  Celery,  17. 
Caterpillar,     Eed-humped     (almond), 

3,      (apple)      6,      (apricot)      10, 

(cherry)    19,    (pear)    41,    (plum, 

prune)  43,  (walnut)  52. 
Caterpillar,  Tent  (apple)   6,   (cherry) 

19,    (peach)    38,    (plum,    prune) 

44,  59. 
Caterpillar,  Yellow-necked,   52. 
Cattle   (Pests  and  parasites),  63. 
Celery,  17. 

Centipede,  Garden,  11. 
Ceratocystis,  49. 
Cercospora  apii  Fr.,  17. 
Cercospora  beticola  Saec,  14. 
Cherry,   18. 

Chloridea  obsoleta  (Fab.),  22. 
Chortophila  hyoscyami  Panzer,  48. 
Chromaphis  juglandicola  (Kalt.),  52. 
Chrysanthemum,  19. 
Chrysobothris  mali  (Horn),  5. 
Chrysomphalus  dictyospermi  Morgan, 

12. 
Cineraria,  19. 
Citrus  fruits,  19. 
Citrus  trees   (nursery),  32. 
Cladosporium  carpophylum  Thiim.,  9. 
Clover  seed  chalsis,  2. 
Coal  tar  creosote  dip,  87. 
Coccomyces  hiemalis,  18. 
Coccus  citricola,  Campb.,  22. 
Cockroaches,  60. 
Coddling  moth  (apple),  4,  (pear)  41, 

(walnut)   51. 
Cold  injury,   55,    (rose)   46. 
Colletotrichum  lindemuihianum  (S.  & 

M.)  B.  &  C,  12. 
Combined  spraying. — See  Spraying. 
Coniothyrium,  15. 
Copper  carbonate,    75;    Ammoniacal 

solution  of,  76;  dust,  27. 
Copper  compounds,  74. 
Copper  sulfate,  75. 
Corn,  22. 

Corn  earworms. — See  Earworms. 
Corrosive  sublimate,  31,  90. 
Corticium  vagum  B.  &  C.  (bean),  12, 

(beet)  14,  (potato)  45. 


Circular  265] 


PLANT  DISEASE  AND  PEST  CONTROL 


99 


Coryneum  beijerinclcii  Oud.  (almond), 
3,  (apricot)  8,  (cherry)  18, 
(peach)  36,  (plum,  prune),  42. 

Cotton,  23. 

Cottony  rot  (citrus),  20. 

Coulure  (grape),  28. 

Creosote  dip,  87. 

Cresylic  acid,  87. 

Crioceris  asparagi  Linn.,  11. 

Crown  gall  (almond),  3,  (apricot)  7, 
(bush  fruits)  15,  (grape)  28, 
(nursery  stock)  32,  (peach)  36, 
(plum,  prune)  42,  (walnut)  51, 
55. 

Crown  wart  (alfalfa),  1. 

Crude  oil  emulsion,  82. 

Cucumber,  23. 

Curly-leaf  (beet),  13. 

Currant,  24. 

Cuscuta  sp.,  1. 

Cutworms  (alfalfa),  2,  (beet)  14, 
(cabbage)  16,  (citrus)  21,  (corn) 
22,  (grain)  28,  (grape)  29, 
(onion)  34,  (pea)  35,  (potato) 
45,   (sorghum,  etc.)   47,  53. 

Cycloconium  oleaginum  Cast.,  33. 

Cydia  pomonella  (Linn.)  (apple),  4, 
(walnut)  51. 

Cylindrosporium,   18. 

Dahlia,  25. 

Damping  off  (citrus  fruits),  20,  (to- 
mato) 50,  55. 

Datana  ministra  Drury,  52. 

Date,  25. 

Deciduous  trees  (nursery),  32. 

Demodex  folliculorum  Simon,  66. 

Diabrotica  soror  Lee,  24. 

Diabrotica  trivittata  Mann,  24. 

Diarthronomyia  hypoqaea  (Low.),  19. 

Dictyocaulus  ftlaria  Rud.,   65. 

Dictyocaulus  viviparus  Bloch.,  64. 

Die-back  (Cherry),  18,  (olive)  33,  57. 

Diplodia  zeae  (Schw.)  Lev.,  22. 

Dipylidium  caninum  Linn.,  66. 

Distillate,  Straight  "tree,"  84. 

Distillate  emulsion,  86. 

Distillate  emulsion,  "Tree,"  83. 

Distillate  emulsion  and  tobacco  ex- 
tract, 85. 

Distillate  emulsions,  Heavy,  84. 

Distillates,  Petroleum,  82. 

Dodder  (alfalfa),  1. 

Dogs(  pests  and  parasites),  66. 

Dothiorella  qregaria  Sacc,  51. 

Downy  mildew. — See  Mildew. 

Dried  fruit  beetle. — See  Beetle. 

Dropping  of  fruit   (fig),  25. 

Drosophila  melanog aster  Meigen.,  26. 

Dry  rot   (olive),  33,  57. 

Ear  mold   (corn),  22. 

Ear  ticks,  63. 


Earthworms,  31. 

Earworm,  Corn  (corn),  22,  (cotton) 
23. 

Eccoptog aster  rugulosus  (Ratz.),  10. 

Eel  worm  (potato),  45,  56. 

Emulsion,  Crude  oil,  82. 

Emulsion,  Distillate,  and  tobacco  ex- 
tract, 85. 

Emulsion,  Kerosene,  83. 

Emulsion,  Tree  distillate,  83. 

Emulsions,  Commercial  prepared,  85. 

Emulsions,  Heavy  distillate,   84. 

Epidiaspis  piricola  Del  G.,  41. 

Epochra  canadensis  Loew.,  24. 

Ergot  of  rye  and  rye  grass,  27. 

Eriophyes  erinea  Nalepa,  52. 

Eriophyes  gracilis   (Nalepa),   16. 

Eriophyes  pyri  (Pagen),  41. 

Eriosoma  languinosa  (Hartig),  41. 

Eriosoma  lanigera  (Hausm.),  6. 

Erysiphe  dehor  earum  D.  C,  23. 

Erysiphe  polygoni  D.  C.  (bean)  12, 
(pea)  35. 

Erysiphe  sp.,  25. 

Erythroneura  comes    (Say),   29. 

Eurymetopon  bicolor  Horn,  51. 

Eurymus  eurytheme  (Boisd.),  2. 

Eutettix  tenella  Baker,  13. 

Exanthema  (olive),  33,  57. 

Exoascus  cerasi  Fuckel,  18. 

Exoascus  deformans  Fcl.,   36. 

Exoascus  pruni  Fcl.,  42. 

Failure  of  flower  buds  to  open  (apri- 
cot), 9. 

Failure  to  grow,  etc.  (nursery  stock), 
32. 

Ferns,  25. 

Fig,  25. 

Fish  oil,  86;  Fish  oil  soap,  86. 

Flea  beetles. — See  Beetles. 

Fleas,  61,  66. 

Flies,  61. 

Flour  paste,  93. 

Flour  paste,  billboard  paste,  93. 

Flo.ur  paste   (spreader),  93. 

Formaldehyde  treatment   (soil),  95. 

Formulas  and  descriptions  of  mate- 
rials, 70. 

EranTcliniella  tritici  (Fitch),  38. 

Frost  injury,  55. 

Frost  scabs  (apricot),  9. 

Fruit  cracking  (apricot),  9. 

Fruit  fly,  Currant  and  gooseberry,  24. 

Fruit  tree  leaf  roller  (apple),  5. 

Fruit  spot,  8. 

Fruit  tree  roller,  41. 

Fuller's  rose  beetle  (citrus),  22  (rose) 
47. 

Fusarium,  55. 

Fusarium  conglutinans  Woll.,  16. 

Fusarium  malli  Taub.,  34. 


100 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fusarium  sp.  (bean),  12,  (beet)  14, 
(corn)  22,  (melon)  32,  (potato) 
45,  (sweet  potato)  50,  (tomato) 
50. 

Fusicladium  (apple),  4,  (pear)  40. 

Fusicladium  eryobotryae  Sciala,  31. 

Fly,  Fruit,— See  Fruit  fly. 

Fly,  Gall.— See  Gall  fly. 

Fly,  Pomace  or  vinegar,  26. 

Gall  fly,    Chrysanthemum,    19. 

Garden  nematode   (potato),  45. 

Glue,  94. 

Glycerine  (in  pear  blight  disinfect- 
ant), 39. 

Gooseberry,  24. 

Gophers,  68. 

Government  whitewash,  91. 

Grafting  wax,  91. 

Grain,  26. 

Grape,  28. 

Grapefruit,  19. 

Grasshoppers  (alfalfa),  2,  (beet)  14, 
(corn)  23,  (grain)  28,  (grape) 
30,  (potato)  45,  (sorghum,  etc.) 
47,  (spinach)  48,  (tomato)  51,56. 

Green  mold  (citrus),  20. 

Green  rot  (apricot),  9. 

Ground  squirrels,  67. 

Gumming  twig  blight,  8. 

Gummosis  (cherry),  18,  (citrus)  20, 
56. 

Gummosis,   Bacterial,    7. 

Gymnoconia  inter stitialis  (Schlect.) 
Lagerh.,  15. 

Haematobia  serrata  B.  D.,  63. 

Haltica  ignita  Illiger,  49. 

Hartigia  cressoni  (Kirby),  15. 

Heat  as  an  insecticide,  94. 

Heliothrips  fasciatus  Perg.  (avocado), 
12,  (bean)  13. 

Heliothrips  haemorrhoidalis  Bouche, 
12. 

Hemerocampa  vetusta  (Boisd.),  6. 

Heterodera  radicicola  Greef.  (beet), 
14,  56. 

Heterodera  schaclitii  Schmidt  (beet), 
14,  56. 

Hollyhock,  30. 

Hop,  30. 

Hoplocampa  coolcei  (Clarke),  18. 

Horn  flies,  63. 

Horntail,  Raspberry  (bush  fruits),  15, 
(rose)  47. 

Hot  water  treatment  (soils,  pots, 
etc.),  95. 

Household  pests  and  animal  parasites, 
60. 

Hyalopterus  arundinis   (Fabr.),  43. 

Hydrocyanic  acid  gas  (grain),  28, 
(formulas,  etc),  89. 

Hylemyia  antiqua  Meig.,   34. 

Hypoderma  lineata  de  Villers,  64. 


Ichneumonidae,  54. 

Insects,  Venemous,   69. 

Inverted  pan  method  (soil  steriliza- 
tion), 95. 

Jelly  end   (potato),  44. 

June  drop   (citrus),  21. 

Knot,  Olive,  33. 

Kerosene,  82. 

Kerosene  emulsion,  83. 

Lawns,  31. 

Lead  arsenate,  Acid,  70. 

Lead  arsenate,  Basic,  70. 

Leaf  and  fruit  spot  (cherry),  18. 

Leaf  curl    (cherry),   18,    (peach)    36. 

Leaf  hopper  (beet),  see  Curly  leaf, 
(grape)  29. 

Leaf  miner  (chrysanthemum),  19, 
(cineraria)    19. 

Leaf  miner,  Beet  or  spinach  (beet), 
14,  (spinach)  48. 

Leaf  perforator,   Cotton,   23. 

Leaf  roller,  Fruit  tree  (apple),  5, 
(apricot)    10,    (plum,  prune)   43. 

Leaf  spot  (alfalfa),  2,  (beet)  14, 
(bush  fruits)  15,  (cherry)  18, 
(plum,  prune)  42,  (strawberry) 
48. 

Leak  (potato),  44. 

Lecanium  cerasorum  Ckll.,  52. 

Lecanium  corni  Bouche,   9. 

Lecanium  pruinosum  Coq.,  52. 

Lemon,  19. 

Leperi'sinus  californicus  Swaine,  34. 

Lepidosaphes  ficus  (Sign.),  26. 

Lepidosaphes  ulmi  (Linn.),  6. 

Leptosphaeria  coniothyrium  Sacc,  15. 

Lice,  67. 

Lice,  Biting,  63. 

Lice,  Sucking,  63. 

Lime-sulfur  dip,  79. 

Lime-sulfur,  Dry,  79. 

Lime-sulfur  solution,  78. 

Lime-sulfur  solution,  Commercial,  78. 

Lime-sulfur  solution,  Homemade,  78. 

Lime-sulfur  wash,   Self-boiled,   78. 

Lime  water  (for  wireworms),  31. 

Little  leaf  (grape),  29,  (peach)  36, 
57. 

Loganberry,  15. 

Loquat,  31. 

Lousej  Mealy  plum,  43. 

Lungworms  (cattle),  64,  (sheep),  65. 

Macrosiphum  pisi  (Kalt.),  35. 

Macrosiphum  rosae   (Linn.),  46. 

Maggot,  Head,  65. 

Maggot,  Onion,  34. 

Maggot,  Wool,  65. 

Mange,  66,  67. 

Mange,  Demodectic,  66,  67. 

Mange,  Follicular,  66. 

Margaropus  annulatus  Say,  64. 


Circular  265] 


PLANT  DISEASE  AND  PEST  CONTROL 


101 


Mealy  bug  (citrus),  22,  (grape)  30, 
Baker's,  40. 

Melaxuma   (walnut),  51. 

Melon,  31. 

Mercuric  chlorid,  90. 

Mercuric  cyanide,  90. 

Mildew  (apple),  4,  (bean)  12,  (cu- 
cumber) 23,  (currant,  goose- 
berry)   24,    (dahlia)   25,    (grape) 

29,  (pea)  35,   (rose)  46. 
Mildew,  Downy   (alfalfa),   1,    (beet) 

14,  (onion)  34,  (pea)  35. 

Mildew,  Powdery  (pea),  35,  (peach) 
36. 

Miscellaneous  (materials  and  formu- 
las), 90. 

Miscible  oil,  86. 

Miscible  oils,  85,   (as  spreaders)   94. 

Mite,  Almond  (almond),  3,  (plum, 
prune)  44. 

Mite,  Blackberry,   16. 

Mite,  European  red    (citrus),   21. 

Mite,  Peach  rust,  37. 

Mite,  Pear  leaf  blister,  41. 

Mite,  Two-spotted  (bean),  13,  (citrus) 
21,  (cucumber)  24,  (currant, 
gooseberry)  24,  (hop)  31,  (straw- 
berry) 49,   (walnut)  52. 

Mite,  Walnut  blister,  52. 

Mites,  Grain,  28. 

Mold,  Ear    (corn),   22. 

Mold,  Fruit,  15. 

Mold,  Gray  (strawberry),  48. 

Monilia  blossom  blight,   8. 

Monilia  brown  rot,   8. 

Monilia  fructigena,  8. 

Monilia  rot  of  ripe  fruit,   8. 

Monilochaetes  infuscans  E.  &  H..  49. 

Mosquitoes,  62. 

Moth,  Angumoise  grain,  28, 

Moth,  Artichoke  plume,  10. 

Moth,  Clothes,  61. 

Moth,  Coddling. — See  Coddling   moth. 

Moth,  Indian  meal  (date),  25,  (raisin) 

30,  (prune)  43,   (walnut)   52. 
Moth,  Potato   tuber,   46. 

Moth,  Strawberry  crown,  48. 

Moth,  Tussock,  6,  44. 

Mottled  leaf  (citrus),  21,  57. 

Mycosphaerella  fragariae  (Tul.)  Linn., 
48. 

Mycosphaerella  pinodes  Berk.  &  Blox., 
35. 

Myzaphis  rosarum   (Walk.),  46. 

Myzus  oraggii  Gill.,  11. 

Myzus  cerasi  Fabr.,  18. 

Myzus  fragaefolii  Ckll.,  48. 

Nematode  (melon),  32,  (nursery 
stock)  32,  (peach)  36,  56. 

Nematode,  Garden  (bean)  13,  (cu- 
cumber) 24,  (potato)  45,  (to- 
mato) 51 


Nematodes  (beet),  14,  (fig),  26. 

Nicodust  and  combinations,  88. 

Nicotine  sulfate,  85,  86,  87,  88. 

Nitrate  of  soda  (for  weeds),  31. 

Notolophus  antiqua  (Linn.),  6. 

Nursery  stock,  32. 

Oak  fungus,  53. 

Oat,  33. 

Oats,  26. 

Oats  (sensitive  to  bluestone),  27. 

Obscure  diseases  (grape),  29. 

Oestrus  ovis  Linn.,  65. 

Oidium,  46. 

Oil  emulsions  (as  spreaders),  94. 

Olive,  33. 

Olive  knot,  33. 

Onion,  34. 

Oospora,  45. 

Orange,   19. 

Ornithodorus  megnini  Duges,  63. 

Otiorhynchus  rugifrons  Gyll.,  49. 

Oyster  shell  scale. — See  scale. 

Pantomorus  fulleri  (Horn),  22. 

Papilio  zolicaon  Boisd.,  17. 

Para-dichloroben*ene,  80. 

Paratetranychus  pilosus  C.  &  F.,  21. 

Paria  canella   (Fabr.),  49. 

Parlatoria  olanchardi  (Targ.),  25. 

Paste,  Dry  billboard,  88. 

Paste,  Flour  and  billboard,  93. 

P  D  B,  80. 

Pea,  35. 

Peach,  36. 

Peach  blight. — See  blight. 

Peach  twig  borer. — See  borer. 

Peacock  spot   (olive),  33. 

Pear,  39. 

Pear  blight. — See  blight. 

Penicillium  sps.    (citrus),   20. 

Peritymbia  vitifoliae  (Fitch),  30. 

Peronospora  schactii  Fcl.,  14. 

Peronospora  schleideni  Ung.,  34. 

Peronospora  trifoliorum  De  Bary  (al- 
falfa)  1,   (pea)   35. 

Petroleum,  Crude,  81. 

Petroleum  distillates,  82. 

Phoenico  coccus  marlatti  Ckll.,  25. 

Pholus  achemon  (Drury),  29. 

Phorbia  brassicae  Bouche,  17. 

Phorodon  humuli  (Schr.),  30. 

Phyllocoptes  cornutus  Banks,  37. 

Phylloxera,  Grape,  30. 

Physiological  diseases  (plum,  prune), 
42,  57. 

Phytomyta  chrysanthemi  Kow.,  19. 

Phytopthora  infestans  (Mont.)  De 
Bary   (potato),  44,   (tomato)   50. 

Phthorimaea  operculella   (Zeller),  46. 

Pink  root  (onion),  34. 

Plant  lice  (ferns),  25. 

Platyptilia  carduidactyla  (Eiley),  10. 

Plenodomus  destruens  Harter,  49. 


102 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Plodia  interpunctella  Hiibn.,  43. 

Plum,  42. 

Plum  pockets,  42. 

Polycaon  confertus  Lee.  (apricot),  9, 
(olive)  33,  (peach)  37. 

Poison  baits,  substitutes  in,  72. 

Poisoned  barley,  92. 

Poisoned  vegetables  for  gophers,  93. 

Polystictis  versicolor  (L.)  Fr.,  4. 

Pontia  rapae  (Linn.),  16. 

Potato,  44. 

Powdery  mildew. — See  mildew. 

Protoparce  quinquemaculata  Haw.,  51. 

Protoparce  sexta  Joh.,  51. 

Prune,  42. 

Pruning  cuts  and  wounds,  Treatment 
of,  58. 

Pseudococcus  (citrus),  22. 

Pseudococcus  odkeri  Essig  (grape), 
30,   (pear)  40. 

Pseudococcus  maritimus  Ehr.  (grape), 
30,  (pear)  40. 

Pseudomonas  juglandis  Pierce,  51. 

Pseudomonas  oleae,  33. 

Pseudomonas  pisi  Sack.,  35. 

Pseudopeziza  medicaginus  (Lib.) 
Sacc,  2. 

Psoroptes  communis  var.  ovis  Hering, 
65. 

Psylliodes  punctulata  Mels.,  30. 

Puccinia  antirrhini  D.  &  H.,  47. 

Puccinia  asparagi  D.  C,  11. 

Puccinia  chrysanthemi  Roze.,   19. 

Puccinia  malvacearum  Mont.,  30. 

Puccinia  pruni  (almond),  3,  (apricot) 
9,  (peach)  36,  (plum,  prune),  42. 

Puccinia  sps.,  26. 

Pumpkin,  31. 

Pythiacystis  citrophthora  S.  &  S.  (avo- 
cado), 11,  (citrus)  20,  (nursery 
stock)   33. 

Pythiacystis  canker  (nursery  stock), 
33. 

Pythiacystis  rot   (citrus),  20. 

Pythium   (potato),  44,  55. 

Rabbits,  69. 

Raisin,  28. 

Ramularia,  48. 

Raspberry,  15. 

Rats,   69. 

Red  humped  caterpillar. — See  cater- 
pillar. 

Red  specking  (apricot),  9. 

Red  spider  (bean),  13,  (cucumber) 
24,  (currant)  24,  (date),  25, 
(hop)  31,  (peach)  38,  (plum, 
prune)   44. 

Red  spider,  Citrus,  43. 

Red  spider,  Common,  44. 

Red  spider  or  almond  mite,  3,  44. 

Resin,  91. 

Resin-Bordeaux  mixture,  75. 


Resin  fish  oil  soap  (as  spreader),  94. 

Resin  wash,  86. 

Rhuoctonia  (bean),  12,  (beet)  14, 
(potato)  44,  55. 

Rhizopus,  44. 

Rhizopus  nigricans  Ehr.,  49. 

Rhopalosiphum  persicae   (Sulz.),  17. 

Rhynchites  licolor  Fabr.,  47. 

Root  maggot,  Cabbage,  17. 

Root  rot,  Armillaria,  53. 

Root  rot,  Seedling,  14. 

Root  worm,  California  grape,  29. 

Rose,  46. 

Rosette,  57. 

Rot,  Black  (sweet  potato),  49. 

Rot,  Blossom  end  (melon),  31,  (to- 
mato) 50,  57. 

Rot,  Botrytis  (strawberry),  48. 

Rot,  Dry    (potato),  45,  57. 

Rot,  Foot  (sweet  potato),  49. 

Rot,  Late  (potato),  44,  (tomato)  50. 

Rot,  Leaf  and  stem  (strawberry),  48. 

Rot,  Soft  (potato),  44,  (sweet  po- 
tato) 49. 

Rot,  Stem   (sweet  potato),  50. 

Roundworms   (dogs),  66,  (swine)   67. 

Rust  (alfalfa),  2,  (almond)  3,  (apri- 
cot) 9,  (asparagus)  11,  (bean)  12, 
(beet)  14,  (chrysanthemum)  19, 
(grain)  26,  (hollyhock)  30, 
(peach)  36,  (plum,  prune)  42, 
(snapdragon)   47. 

Rust,  Orange  (bush  fruits),  15. 

Rye  and  Rye  grass,  27. 

Saissetia  oleae  (Bern.),  9,  33. 

Salt  (as  tree  killer),  96. 

San  Jose  scale. — See  scale. 

Sappy  bark  (apple),  4. 

Sarcoptes  scaoiei  var,  canis  Linn.,  66. 

Sawfly,  Cherry  fruit  (cherry),  18, 
(plum,  prune)   43. 

Scab  (apple),  4,  (apricot)  9,  (loquat) 
31,    (pear)    40,    (potato)    45. 

Scab    (sheep),   65. 

Scabies  (dog),  66,  (swine)  67. 

Scale,  Black  (apricot),  9,  (ferns)  25, 
(plum,  prune)  42. 

Scale,  Brown  apricot  (apricot),  9, 
(peach)   37,    (plum,  prune)  42. 

Scale,  Cherry  or  calico  (walnut),  52. 

Scale,  Date  palm,  25. 

Scale,  Frosted,  52. 

Scale,  insects    (citrus),   22. 

Scale,  Italian  pear  (pear),  41,  (plum, 
prune)  43. 

Scale,  Ivy  or  oleander  (olive),  34. 

Scale,  Marlatt,  25. 

Scale,  Mediterranean  fig,  26. 

Scale,  Oyster  shell  (apple),  6. 

Scale,  Rose  (bush  fruits),  16,  (rose) 
47. 


Circular  265] 


PLANT  DISEASE  AND  PEST   CONTROL 


103 


Scale,  San  Jose  (almond),  3,  (apple) 

6,   (currant,  gooseberry)   24,   (lo- 

quat)  31,  (peach)   38,  (pear)  41, 

(plum,  prune)  44. 
Scale,  Spanish  red,  12. 
Scales,  brown  apricot  and  other  soft 

(pear),  40. 
Scaly  bark  (citrus),  21. 
Schuura  concinna  S.  &  H.,  43. 
Scirtothrips  citri  (Moult.),  21. 
Sclerotinia     cinerea     (Bon.)     Schrot. 

(apricot),   8,    (peach)    36. 
Sclerotinia  fructigena,  8. 
Sclerotinia  libertiana   Fcl.    (almond), 

2,   (apricot)   9,   (citrus)   20,   (fig) 

26. 
Scullions   (onion),  34. 
Scurf  (sweet  potato),  49. 
Scutigerella  calif ornica  (Woodw.),  11 
Septoria  rubi  West,  15. 
Scptoria  petroseleni  Desm.,  17. 
Sheep   (pests  and  parasites),  65. 
Shot  hole   (almond),  3,  (apricot)   8. 
Silver  fish  moth,  62. 
Siphocoryne   capreae    (Fab.),    17. 
Sitotroga  cerealla  Oliv.,  28. 
Slug,  Cherry  (cherry),  19. 
Slug,  Cherry  or  pear   (pear),  40. 
Slugs,  57. 

Smut   (fig),  26,  (grain)  26. 
Smut,  Boil  or  common  (corn),  22. 
Smut,  Head   (sorghum,  etc.),  47. 
Smut,  Kernel   (grain),  27,   (sorghum, 

etc.)    47. 
Smuts,  Loose  (grain),  27. 
Snails,  57. 
Snapdragon,  47. 
Soap   (as  spreader),  94. 
Soap,  Hard,  83. 
Soap,  Liquid,  83. 
Sodium  arsenite,  72. 
Sodium  arsenite   (as  tree  killer),  96. 
Sodium  cyanid,  89. 
Soil  disinfection,  95. 
Soil  injury  (avocado),  12. 
Sorghum,  47. 
Sorghums   and    Sudan    grass,    Kernel 

smut  of,  27,  47. 
Sour   sap    (almond),    3,    (apricot)    7, 

(cherry)  18,  (plum,  prune)  42,  57. 
Souring  (fig),  26. 
Sow  bugs,  62. 
Sphacelotheca  reiliana  (Kiihn.)  Clint., 

47. 
Sphacelotheca  sorghi  (Lk.)  CI.,  47. 
Sphaeronema   fimoriatum    (E.    &    H.) 

Sacc,  49. 
Sphaerotheca  humuli  (D.  C.)  Burr.,  46. 
Sphaerotheca  leucotricha    (E.    &    E.) 

Salm.,  4. 
Sphaerotheca  mors-uvae  (Schw.)  B.  & 

C,  24. 


Sphaerotheca  oxyacanthae  (De  C.)  De 

B,  4. 
Sphaerotheca  pannosa   (Wallr.)    Lev., 

46. 
Sphaerotheca  pannosa     var.     persicae 

(Wallr.)  Lev.,  36. 
Sphinx  moth,  Achemon,  29. 
Spiders,  69. 
Spinach,  48. 
Splitting  (fig),  26. 
Spot  (pea),  35. 
Spraying,      Combined      (almond,      4, 

(apple)  6,  (apricot)  10,  (currant, 

gooseberry)      24,      (peach)      39, 

(pear)     42,     (plum,    prune)     44, 

(potato)  46,  (rose)  47. 
Spreaders,  93. 
Squash,  31. 
Squash  bug,  32. 
Squirrels,  Ground,  67. 
Steam  cooking  (soil),  95. 
Stem  rot  (alfalfa),  2,  (bean)  12. 
Sterigmatocystis  ficum  (Reich.)  Henn., 

26. 
Strawberry,  48. 
Strychnine-coated  barley,  92. 
Sudan  grass,  47. 

Sudan  grass,  Kernel  smut  of,  27,  47. 
Sulfides,  Alkali,  79. 
Sulfur  and  sulfur  compounds,  76. 
Sulfur,  Dry,  76. 
Sulfur-nicodust,  88. 
Sulfur  pastes,  77. 
Sulfurs,  Wettable,  77. 
Sunburn,  59. 

Surface  firing  (soil  disinfection),  95. 
Sweet  potato,  49. 
Swine  (pests  and  parasites),  67. 
Taeniothrips  inconsequent  Uzel.,  41. 
Tapeworms,  66. 

Tent  caterpillars. — See  caterpillars. 
Tetranychus  oimaculatus  Harvey,  21. 
Tetranychus    telarius    Linn,     (bean), 

13,      (currant,     gooseberry)      24, 

(plum,   prune)    44,    (strawberrv) 

49. 
Thrips,  Bean    (avocado),  12,    (bean) 

13,    (cotton)   23. 
Thrips,  Citrus,  21. 
Thrips,  Greenhouse  (avocado),  12. 
Thrips,  Onion,  34. 
Thrips,  Pear  (cherry)   19,   (pear)  41, 

(plum,  prune)   43. 
Thrips  taoaci  Lind.,  34. 
Thrips,  Wheat    (peach),   38. 
Ticks,  64. 
Tilletia  sps.,  26. 
Tobacco,  50. 
Tobacco  dust,  88. 
Tobacco  extract,  85. 
Tobacco  preparations,  87. 
Tomato,  50. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Toxascaris  limbata  R.  &  H.,  66. 
Transchelia    punctata    (Pers.)     Arth. 

(almond)  3,  (apricot)  9,  (peach) 

36,  (plum,  prune)  42. 
"Tree"  distillate,  83,  84. 
Tree  killers,  96. 
Trichobaris  trinotata  Say,  46. 
Trichodectes  scalarius  Nitzsch.,  63. 
Tuberculosis   (olive),  33. 
Tussock  moths  (apple),  6,  44. 
Tyroglyphus  sps.,  28. 
Uncinula  necator  (Schw.)  Burr.,  29. 
Uncinula  spiralis  B.  &  C,  29. 
Unfruitfulness  (almond),  3,  (apricot) 

9,  (plum,  prune)  42. 
Uromyces     appendiculatus      (Per  s.) 

Link.,  12. 
Uromyces  oetae   (Pers.)  Kiihn.,  14. 
Uromyces  striatus  Schr.,  2. 
Urophlyctis  alfalfae  (Lag.)  Magn.,  1. 
Ustilago  sps.,  26. 
Ustilago  zeae  (Beckm.)  Ung.,  22. 
Vacuum  fumigation,  89. 
Vanessa  caryae  Hiibn.,  30. 
Venturia  inequalis  (Cke.)  Wint.,  4. 
Venturia  pyrina  Aderh.,  40. 
Verticillium  caulophagus  (Law.),  15. 
Walnut,  51. 
Warbles,  64. 

Water  injury   (avocado),   12. 
Watermelon,  31. 


Wax,  Grafting,  91. 

Weeds   (lawns),  31. 

Weed  killers,  96. 

Weevil  —  Bean,  13;  Granary,  28; 
Granary  and  rice,  23,  47;  Pea, 
35;  Rice,  28;  Strawberry  root, 
49. 

Wettable    sulfurs,   77. 

Wheat,  26. 

Whitewash,  90,  91. 

Whitewash,  Government,  91. 

Wilt  (alfalfa),  2,  (bean)  12,  (cab- 
bage) 16,  (melon)  32,  (potato) 
45,  (sweet  potato)  50,  (tomato) 
50. 

Winter  injury,  57. 

Winter  killing  (walnut),  51. 

Wireworms  (bean),  13,  (beet)  14, 
(corn)  23,  (lawns)  31,  (onions) 
34,   (potato)  46,  59. 

Wood  decay  (apricot),  7,  (cherry) 
18,  (citrus)  20,  (olive)  33, 
(peach)  36,  (plum,  prune)  42, 
(walnut)  51. 

Wood  decay  prevention,  58. 

Worm,  Cabbage,  16;  Tobacco,  51; 
Tomato,  51. 

Worms,  Tomato  and  tobacco,  46. 

Xyleborus  xylographus  Say,  10. 

Xylotrechus  nauticus  Mann,  52. 

Yellows  (cabbage),  16. 

Zinc  arsenite,  71. 


